Thee Ei Khaing Shwe, Tatsuya Asaji, Ryota Kimura, Daisuke Iida, Mohammed A. Najmi, Kazuhiro Ohkawa, Yoshihiro Ishitani
Microscopic lattice vibration images of the E2(high) mode (E2H) and another mode of A1(LO) (A1L) or the higher energy branch of LO‐phonon−plasmon coupling mode (LOPC+) in a Ga0.95In0.05N film on a GaN template are obtained by Raman scattering spectroscopy using a 325 nm laser. The increase in temperature by increasing the laser power is obtained from the decrease in the energy of E2H and the theoretical formula comprising two terms based on the mode energy variation of the bulk material and the thermal strain effect. Using the obtained temperature and the energy shift of the LOPC+, the mapping images of the temperature and electron density in the x–y plane are simultaneously obtained. This image provides the spatial variation of photoluminescence (PL) emission efficiency, given as PL intensity per electron. This method enables the quantitative discussion on photo‐emission efficiency even in the regions of low or high carrier density affected by carrier transport. In the investigated area, a region with a lower PL efficiency is found despite a higher electron density and lower temperature increase than the surrounding region. This imaging analysis is feasible in integrating the carrier and thermal energy transports and recombination processes in carrier dynamics study.
{"title":"Photoluminescence Emission Efficiency Analysis Methodology by Integrating Raman Spectroscopy of the A1(LO) and E2(high) Phonons in a GaInN/GaN Heterostructure","authors":"Thee Ei Khaing Shwe, Tatsuya Asaji, Ryota Kimura, Daisuke Iida, Mohammed A. Najmi, Kazuhiro Ohkawa, Yoshihiro Ishitani","doi":"10.1002/pssb.202400057","DOIUrl":"https://doi.org/10.1002/pssb.202400057","url":null,"abstract":"Microscopic lattice vibration images of the E<jats:sub>2</jats:sub>(high) mode (E<jats:sub>2</jats:sub><jats:sup>H</jats:sup>) and another mode of A<jats:sub>1</jats:sub>(LO) (A<jats:sub>1</jats:sub><jats:sup>L</jats:sup>) or the higher energy branch of LO‐phonon−plasmon coupling mode (LOPC+) in a Ga<jats:sub>0.95</jats:sub>In<jats:sub>0.05</jats:sub>N film on a GaN template are obtained by Raman scattering spectroscopy using a 325 nm laser. The increase in temperature by increasing the laser power is obtained from the decrease in the energy of E<jats:sub>2</jats:sub><jats:sup>H</jats:sup> and the theoretical formula comprising two terms based on the mode energy variation of the bulk material and the thermal strain effect. Using the obtained temperature and the energy shift of the LOPC+, the mapping images of the temperature and electron density in the <jats:italic>x</jats:italic>–<jats:italic>y</jats:italic> plane are simultaneously obtained. This image provides the spatial variation of photoluminescence (PL) emission efficiency, given as PL intensity per electron. This method enables the quantitative discussion on photo‐emission efficiency even in the regions of low or high carrier density affected by carrier transport. In the investigated area, a region with a lower PL efficiency is found despite a higher electron density and lower temperature increase than the surrounding region. This imaging analysis is feasible in integrating the carrier and thermal energy transports and recombination processes in carrier dynamics study.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"106 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140811837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The internal quantum efficiency (IQE) and cathodoluminescence intensity line profile of AlGaN multiple quantum well (MQW) structures on low‐dislocation face‐to‐face annealed sputtered AlN (FFA Sp‐AlN) and on conventional metalorganic vapor‐phase epitaxy‐grown AlN (MOVPE‐AlN) templates are evaluated and the effect of the number of quantum wells (QWs) on the IQE is discussed. The higher IQE in the FFA samples is probably due to the lower threading dislocation (TD) density; however, the IQE also increases with the number of QWs although the TD density remains constant. Effective diffusion length increases with the number of QWs, indicating that the AlGaN MQW layer helps to suppress point defect diffusion, resulting in IQE increase. Furthermore, the segregation of point defects into the TDs and point defect diffusion via the TDs may explain the difference in the IQE improvement rate between the MQWs on the FFA Sp‐AlN and MOVPE‐AlN templates.
{"title":"Well Number Dependence of Internal Quantum Efficiency in AlGaN Quantum Wells on Low‐Dislocation Sputtered AlN Templates","authors":"Kosuke Inai, Ryota Oshimura, Kunio Himeno, Megumi Fujii, Yuta Onishi, Satoshi Kurai, Narihito Okada, Kenjiro Uesugi, Hideto Miyake, Yoichi Yamada","doi":"10.1002/pssb.202300567","DOIUrl":"https://doi.org/10.1002/pssb.202300567","url":null,"abstract":"The internal quantum efficiency (IQE) and cathodoluminescence intensity line profile of AlGaN multiple quantum well (MQW) structures on low‐dislocation face‐to‐face annealed sputtered AlN (FFA Sp‐AlN) and on conventional metalorganic vapor‐phase epitaxy‐grown AlN (MOVPE‐AlN) templates are evaluated and the effect of the number of quantum wells (QWs) on the IQE is discussed. The higher IQE in the FFA samples is probably due to the lower threading dislocation (TD) density; however, the IQE also increases with the number of QWs although the TD density remains constant. Effective diffusion length increases with the number of QWs, indicating that the AlGaN MQW layer helps to suppress point defect diffusion, resulting in IQE increase. Furthermore, the segregation of point defects into the TDs and point defect diffusion via the TDs may explain the difference in the IQE improvement rate between the MQWs on the FFA Sp‐AlN and MOVPE‐AlN templates.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"36 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140811808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Herein, triangular‐lattice nanopillar templates are fabricated on sputter‐deposited AlN/Si (111) substrates. Nanotemplate selective‐area growth via radiofrequency‐plasma‐assisted molecular beam epitaxy is employed to grow GaN nanocolumns on the nanopillars. Well‐ordered uniform GaN nanocolumn arrays are obtained by inserting a migration‐enhanced‐epitaxy grown AlN/AlGaN buffer layer, thereby aligning the polarity of GaN to Ga‐polar. Subsequently, bulk InGaN active layers are grown on top of the GaN nanocolumns with increasing growth time (tg = 10–20 min). In the initial stage of growth (tg = 10 min), low‐In‐content InGaN grows on the edges of the six‐sided pyramidal top of the GaN nanocolumns. As the growth progresses, low‐In‐composition InGaN fills the sides between InGaN on the edges, while high‐In‐composition InGaN rapidly grows on the top of the c‐plane nanocolumns. High‐angle annular dark‐field scanning transmission electron microscopy reveals the formation of an InGaN core, covered with a low‐In‐composition InGaN shell, on the top of the nanocolumns. At tg = 20 min, the photoluminescence spectrum exhibits a peak at 669 nm with a full width at half maximum value of 51.7 nm. Thus, the proposed method is suitable for growing red‐light‐emitting well‐ordered InGaN/GaN nanocolumn arrays on Si.
{"title":"Red Emission of Well‐Ordered InGaN/GaN Nanocolumn Arrays on Si (111) Substrates Grown via Nanotemplate Selective‐Area Growth","authors":"Kota Hoshino, Rie Togashi, Katsumi Kishino","doi":"10.1002/pssb.202400064","DOIUrl":"https://doi.org/10.1002/pssb.202400064","url":null,"abstract":"Herein, triangular‐lattice nanopillar templates are fabricated on sputter‐deposited AlN/Si (111) substrates. Nanotemplate selective‐area growth via radiofrequency‐plasma‐assisted molecular beam epitaxy is employed to grow GaN nanocolumns on the nanopillars. Well‐ordered uniform GaN nanocolumn arrays are obtained by inserting a migration‐enhanced‐epitaxy grown AlN/AlGaN buffer layer, thereby aligning the polarity of GaN to Ga‐polar. Subsequently, bulk InGaN active layers are grown on top of the GaN nanocolumns with increasing growth time (<jats:italic>t</jats:italic><jats:sub>g</jats:sub> = 10–20 min). In the initial stage of growth (<jats:italic>t</jats:italic><jats:sub>g</jats:sub> = 10 min), low‐In‐content InGaN grows on the edges of the six‐sided pyramidal top of the GaN nanocolumns. As the growth progresses, low‐In‐composition InGaN fills the sides between InGaN on the edges, while high‐In‐composition InGaN rapidly grows on the top of the c‐plane nanocolumns. High‐angle annular dark‐field scanning transmission electron microscopy reveals the formation of an InGaN core, covered with a low‐In‐composition InGaN shell, on the top of the nanocolumns. At <jats:italic>t</jats:italic><jats:sub>g</jats:sub> = 20 min, the photoluminescence spectrum exhibits a peak at 669 nm with a full width at half maximum value of 51.7 nm. Thus, the proposed method is suitable for growing red‐light‐emitting well‐ordered InGaN/GaN nanocolumn arrays on Si.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"51 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael Bonitz, Jan‐Philip Joost, Christopher Makait, Erik Schroedter, Tim Kalsberger, Karsten Balzer
The theory of nonequilibrium Green functions (NEGF) has seen a rapid development over the recent three decades. Applications include diverse correlated many‐body systems in and out of equilibrium. Very good agreement with experiments and available exact theoretical results could be demonstrated if the proper selfenergy approximations were used. However, full two‐time NEGF simulations are computationally costly, as they suffer from a cubic scaling of the computation time with the simulation duration. Recently the G1–G2 scheme that exactly reformulates the generalized Kadanoff–Baym ansatz with Hartree–Fock propagators (HF‐GKBA) into time‐local equations is introduced, which achieves time‐linear scaling and allows for a dramatic speedup and extension of the simulations (Schluenzen et al. Phys. Rev. Lett. 2020, 124, 076601). Remarkably, this scaling is achieved quickly, and also for high‐level selfenergies, including the nonequilibrium GW and T‐matrix approximations (Joost et al. Phys. Rev. B 2020, 101, 245101). Even the dynamically screened ladder approximation is now feasible (Joost et al. Phys. Rev. B 2022, 105, 165155), and also applications to electron‐boson systems are demonstrated. Herein, an overview on recent results that are achieved with the G1–G2 scheme is presented. Problems and open questions are discussed and further ideas of how to overcome the current limitations of the scheme and present are presented. The G1–G2 scheme is illustrated by presenting applying it to the excitation dynamics of Hubbard clusters, to optical excitation of graphene, and to charge transfer during stopping of ions by correlated materials.
近三十年来，非平衡格林函数（NEGF）理论得到了快速发展。其应用包括平衡和非平衡状态下的各种相关多体系统。如果使用适当的自能近似值，可以证明与实验和现有精确理论结果非常吻合。然而，全双时 NEGF 模拟的计算成本很高，因为它们的计算时间与模拟持续时间成立方比例关系。最近推出的 G1-G2 方案将广义卡达诺夫-贝姆方差与哈特里-福克传播者（HF-GKBA）精确地重新表述为时域方程，实现了时间-线性缩放，使模拟的速度和扩展性大大提高（Schluenzen 等人，Phys. Rev. Lett.）值得注意的是，这种缩放是快速实现的，也适用于高级自能，包括非平衡 GW 和 T 矩阵近似（Joost 等人，Phys. Rev. B 2020, 101, 245101）。即使是动态屏蔽梯形近似现在也是可行的（Joost 等人，Phys. Rev. B 2022, 105, 165155），而且在电子玻色子系统中的应用也得到了证明。在此，我们将概述使用 G1-G2 方案所取得的最新成果。讨论了存在的问题和未决问题，并就如何克服该方案目前的局限性提出了进一步的想法。通过将 G1-G2 方案应用于哈伯德团簇的激发动力学、石墨烯的光学激发以及相关材料阻止离子期间的电荷转移，对该方案进行了说明。
{"title":"Accelerating Nonequilibrium Green Functions Simulations: The G1–G2 Scheme and Beyond","authors":"Michael Bonitz, Jan‐Philip Joost, Christopher Makait, Erik Schroedter, Tim Kalsberger, Karsten Balzer","doi":"10.1002/pssb.202300578","DOIUrl":"https://doi.org/10.1002/pssb.202300578","url":null,"abstract":"The theory of nonequilibrium Green functions (NEGF) has seen a rapid development over the recent three decades. Applications include diverse correlated many‐body systems in and out of equilibrium. Very good agreement with experiments and available exact theoretical results could be demonstrated if the proper selfenergy approximations were used. However, full two‐time NEGF simulations are computationally costly, as they suffer from a cubic scaling of the computation time with the simulation duration. Recently the G1–G2 scheme that exactly reformulates the generalized Kadanoff–Baym ansatz with Hartree–Fock propagators (HF‐GKBA) into time‐local equations is introduced, which achieves time‐linear scaling and allows for a dramatic speedup and extension of the simulations (Schluenzen et al. <jats:italic>Phys. Rev. Lett.</jats:italic> 2020, <jats:italic>124</jats:italic>, 076601). Remarkably, this scaling is achieved quickly, and also for high‐level selfenergies, including the nonequilibrium GW and <jats:italic>T</jats:italic>‐matrix approximations (Joost et al. <jats:italic>Phys. Rev. B</jats:italic> 2020, <jats:italic>101</jats:italic>, 245101). Even the dynamically screened ladder approximation is now feasible (Joost et al. <jats:italic>Phys. Rev. B</jats:italic> 2022, <jats:italic>105</jats:italic>, 165155), and also applications to electron‐boson systems are demonstrated. Herein, an overview on recent results that are achieved with the G1–G2 scheme is presented. Problems and open questions are discussed and further ideas of how to overcome the current limitations of the scheme and present are presented. The G1–G2 scheme is illustrated by presenting applying it to the excitation dynamics of Hubbard clusters, to optical excitation of graphene, and to charge transfer during stopping of ions by correlated materials.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"50 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140806167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
α‐Ga2O3 is a suitable material for UV‐C optical devices owing to its optical absorption edge wavelength. In this study, α‐Ga2O3 thin films are grown on c‐, a‐, m‐, n‐, and r‐oriented sapphire substrates by mist chemical vapor deposition. Furthermore, their structural fluctuations, (normal direction of the surface) and (rotational direction on the surface), are examined. As a result, the a‐oriented α‐Ga2O3 thin films exhibit the smallest and . Based on the results of the previous examination, metal–semiconductor–metal (MSM) photodetectors are fabricated using c‐ and a‐oriented α‐Ga2O3 thin films and their photoconducting properties are characterized. Under D2 lamp light illumination, the MSM photodetector using a‐oriented films produces photocurrent four to six times greater than those using c‐oriented films. The visible‐light rejection ratios are at 10 V and 105.2 at 24 V. The photoresponsivity is estimated to be 2.2 A W−1 under the illumination of a D2 UV lamp and 24 V bias voltage. In these results, it is suggested that the a‐oriented α‐Ga2O3 thin film exhibits a higher in‐plane carrier mobility than the c‐oriented film. Thus, a‐oriented α‐Ga2O3 films are more suitable than c‐oriented α‐Ga2O3 films for fabricating MSM photodetectors.
α-Ga2O3具有光吸收边缘波长，是紫外-C光学器件的理想材料。本研究采用雾化化学气相沉积法在 c、a、m、n 和 r 向蓝宝石基底上生长了 α-Ga2O3 薄膜。此外，还研究了它们的结构波动（表面法线方向）和（表面旋转方向）。结果表明，a 方向的 α-Ga2O3 薄膜表现出最小的结构波动，而 r 方向的 α-Ga2O3 薄膜表现出最小的结构波动。根据之前的研究结果，利用 c 向和 a 向 α-Ga2O3 薄膜制作了金属-半导体-金属（MSM）光电探测器，并对其光导特性进行了表征。在 D2 灯照射下，使用 a 向薄膜的 MSM 光电探测器产生的光电流是使用 c 向薄膜的 MSM 光电探测器的四至六倍。在 D2 紫外灯和 24 V 偏置电压的照射下，光致发射率估计为 2.2 A W-1。这些结果表明，a 向 α-Ga2O3 薄膜比 c 向薄膜具有更高的面内载流子迁移率。因此，a 向 α-Ga2O3 薄膜比 c 向 α-Ga2O3 薄膜更适合用于制造 MSM 光电探测器。
{"title":"Improvement of Photoconductivity in a‐Oriented α‐Ga2O3 Thin Films Grown on Sapphire Substrates by Mist Chemical Vapor Deposition","authors":"Kazuyuki Uno, Keishi Yamaoka","doi":"10.1002/pssb.202300463","DOIUrl":"https://doi.org/10.1002/pssb.202300463","url":null,"abstract":"<jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> is a suitable material for UV‐C optical devices owing to its optical absorption edge wavelength. In this study, <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> thin films are grown on c‐, a‐, m‐, n‐, and r‐oriented sapphire substrates by mist chemical vapor deposition. Furthermore, their structural fluctuations, (normal direction of the surface) and (rotational direction on the surface), are examined. As a result, the a‐oriented <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> thin films exhibit the smallest and . Based on the results of the previous examination, metal–semiconductor–metal (MSM) photodetectors are fabricated using c‐ and a‐oriented <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> thin films and their photoconducting properties are characterized. Under D<jats:sub>2</jats:sub> lamp light illumination, the MSM photodetector using a‐oriented films produces photocurrent four to six times greater than those using c‐oriented films. The visible‐light rejection ratios are at 10 V and 10<jats:sup>5.2</jats:sup> at 24 V. The photoresponsivity is estimated to be 2.2 A W<jats:sup>−1</jats:sup> under the illumination of a D<jats:sub>2</jats:sub> UV lamp and 24 V bias voltage. In these results, it is suggested that the a‐oriented <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> thin film exhibits a higher in‐plane carrier mobility than the c‐oriented film. Thus, a‐oriented <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films are more suitable than c‐oriented <jats:italic>α</jats:italic>‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films for fabricating MSM photodetectors.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"55 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To investigate nonradiative recombination processes in indium gallium nitride (InGaN)‐based red light‐emitting diodes (LEDs), an InGaN‐based red LED with a hybrid quantum well (QW) structure consisting of red and blue single quantum wells (SQWs) is characterized by micro‐photoluminescence (μ‐PL) spectroscopy. The μ‐PL mapping of the red emission reveals numerous dark spots with various sizes and contrasts. Not only the red and blue (from a blue SQW) but green emission bands are observed at some red dark spots, suggesting that indium (In) segregation is one of the causes of nonradiative recombination in the red emission. Comparing the blue and green emission images to the red emission image reveals that the dark spots in the intensity map of the red emission can be classified into four types. Through this correlative analysis, the red dark spots associated with the dark areas in the intensity map of the blue emission are attributed to the major nonradiative recombination centers in the red emission.
为了研究基于氮化铟镓（InGaN）的红色发光二极管（LED）中的非辐射重组过程，我们利用微光致发光（μ-PL）光谱对一种基于氮化铟镓（InGaN）的红色 LED 进行了表征，该 LED 具有由红色和蓝色单量子阱（SQW）组成的混合量子阱（QW）结构。红色发射的 μ-PL 图显示了许多不同大小和对比度的暗点。在一些红色暗点上不仅能观察到红色和蓝色（来自蓝色 SQW）发射带，还能观察到绿色发射带，这表明铟（In）偏析是红色发射中非辐射重组的原因之一。将蓝色和绿色发射图像与红色发射图像进行比较，可以发现红色发射强度图中的暗点可分为四种类型。通过这种关联分析，与蓝色发射强度图中暗区相关的红色暗点可归因于红色发射中的主要非辐射重组中心。
{"title":"Correlative Micro‐Photoluminescence Study on Hybrid Quantum‐Well InGaN Red Light‐Emitting Diodes","authors":"Zhaozong Zhang, Ryota Ishii, Kanako Shojiki, Mitsuru Funato, Daisuke Iida, Kazuhiro Ohkawa, Yoichi Kawakami","doi":"10.1002/pssb.202400036","DOIUrl":"https://doi.org/10.1002/pssb.202400036","url":null,"abstract":"To investigate nonradiative recombination processes in indium gallium nitride (InGaN)‐based red light‐emitting diodes (LEDs), an InGaN‐based red LED with a hybrid quantum well (QW) structure consisting of red and blue single quantum wells (SQWs) is characterized by micro‐photoluminescence (<jats:italic>μ</jats:italic>‐PL) spectroscopy. The <jats:italic>μ</jats:italic>‐PL mapping of the red emission reveals numerous dark spots with various sizes and contrasts. Not only the red and blue (from a blue SQW) but green emission bands are observed at some red dark spots, suggesting that indium (In) segregation is one of the causes of nonradiative recombination in the red emission. Comparing the blue and green emission images to the red emission image reveals that the dark spots in the intensity map of the red emission can be classified into four types. Through this correlative analysis, the red dark spots associated with the dark areas in the intensity map of the blue emission are attributed to the major nonradiative recombination centers in the red emission.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"21 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The strain relaxation, surface morphology, and reflectivity of AlGaN‐distributed Bragg reflectors (DBRs) grown via metal–organic chemical vapor deposition on AlN/Al2O3 templates are investigated. Strain relaxation begins in a 10‐period Al0.50Ga0.50N (27 nm)/Al0.75Ga0.25N (29 nm) DBR, and the degree of strain relaxation (DSR) increases with the number of DBR periods. The 30‐period DBR exhibits a peak reflectivity of 0.82 at 279 nm, with a stopband of 12 nm. The DSR of n‐Al0.62Ga0.38N on the 30‐period DBR increases from 70% to 100% as the n‐Al0.62Ga0.38N thickness increases from 0.4 to 2.5 μm. Although the surface of a DBR comprises numerous spiral hillocks, n‐Al0.62Ga0.38N grown on an AlGaN DBR exhibits a step‐flow growth. A DSR of 100% with threading screw dislocations of 2.0 × 108 cm−2 and threading edge dislocations of 1.2 × 109 cm−2 is obtained for a 2.5 μm‐thick n‐Al0.62Ga0.38N on a 30‐period AlGaN DBR.
{"title":"Metal–Organic Chemical Vapor Deposition of n‐AlGaN Grown on Strain‐Relaxed Distributed Bragg Reflector Buffer Layers","authors":"Hisashi Yamada, Naoto Kumagai, Toshikazu Yamada","doi":"10.1002/pssb.202300558","DOIUrl":"https://doi.org/10.1002/pssb.202300558","url":null,"abstract":"The strain relaxation, surface morphology, and reflectivity of AlGaN‐distributed Bragg reflectors (DBRs) grown via metal–organic chemical vapor deposition on AlN/Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> templates are investigated. Strain relaxation begins in a 10‐period Al<jats:sub>0.50</jats:sub>Ga<jats:sub>0.50</jats:sub>N (27 nm)/Al<jats:sub>0.75</jats:sub>Ga<jats:sub>0.25</jats:sub>N (29 nm) DBR, and the degree of strain relaxation (DSR) increases with the number of DBR periods. The 30‐period DBR exhibits a peak reflectivity of 0.82 at 279 nm, with a stopband of 12 nm. The DSR of <jats:italic>n</jats:italic>‐Al<jats:sub>0.62</jats:sub>Ga<jats:sub>0.38</jats:sub>N on the 30‐period DBR increases from 70% to 100% as the <jats:italic>n</jats:italic>‐Al<jats:sub>0.62</jats:sub>Ga<jats:sub>0.38</jats:sub>N thickness increases from 0.4 to 2.5 μm. Although the surface of a DBR comprises numerous spiral hillocks, <jats:italic>n</jats:italic>‐Al<jats:sub>0.62</jats:sub>Ga<jats:sub>0.38</jats:sub>N grown on an AlGaN DBR exhibits a step‐flow growth. A DSR of 100% with threading screw dislocations of 2.0 × 10<jats:sup>8</jats:sup> cm<jats:sup>−2</jats:sup> and threading edge dislocations of 1.2 × 10<jats:sup>9</jats:sup> cm<jats:sup>−2</jats:sup> is obtained for a 2.5 μm‐thick <jats:italic>n</jats:italic>‐Al<jats:sub>0.62</jats:sub>Ga<jats:sub>0.38</jats:sub>N on a 30‐period AlGaN DBR.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"7 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140635432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The photoluminescence (PL) of self‐trapped holes (STH) in ultra‐wide bandgap β‐Ga2O3 is commonly its most dominant light emission and is an inherent property. Thus, gaining knowledge of the crystal dynamics that impact the PL properties is vital to sensor and other technologies. The PL, Raman‐phonons, and their interactions are studied at an extreme temperature range of 77–622 K. The PL is studied up to the bandgap value of ≈5 eV. It is found that the high‐energy Raman modes provide a major route to the nonradiative process of the PL via STH–phonon interaction with an activation energy of 72 meV. This dynamic is modeled with the configurational coordinate scheme at the strong phonon coupling limit. The exceptionally broad Gaussian PL linewidth manifests this coupling. The weak temperature response of the PL energy peak position indicates that the STH has characteristics of a deep‐level defect. This contrasts with the large redshift of ≈220 meV of the optical gap of the film, ascertained from transmission. Unlike the temperature response of the high‐energy phonons, the behavior of the low‐energy phonons is found to follow the Bose–Einstein population increase, indicating no strong interaction with the STH.
{"title":"The Nonradiative Properties of Self‐Trapped Holes in Ultra‐Wide Bandgap Gallium Oxide Film","authors":"Isiaka Lukman, Leah Bergman","doi":"10.1002/pssb.202300590","DOIUrl":"https://doi.org/10.1002/pssb.202300590","url":null,"abstract":"The photoluminescence (PL) of self‐trapped holes (STH) in ultra‐wide bandgap β‐Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> is commonly its most dominant light emission and is an inherent property. Thus, gaining knowledge of the crystal dynamics that impact the PL properties is vital to sensor and other technologies. The PL, Raman‐phonons, and their interactions are studied at an extreme temperature range of 77–622 K. The PL is studied up to the bandgap value of ≈5 eV. It is found that the high‐energy Raman modes provide a major route to the nonradiative process of the PL via STH–phonon interaction with an activation energy of 72 meV. This dynamic is modeled with the configurational coordinate scheme at the strong phonon coupling limit. The exceptionally broad Gaussian PL linewidth manifests this coupling. The weak temperature response of the PL energy peak position indicates that the STH has characteristics of a deep‐level defect. This contrasts with the large redshift of ≈220 meV of the optical gap of the film, ascertained from transmission. Unlike the temperature response of the high‐energy phonons, the behavior of the low‐energy phonons is found to follow the Bose–Einstein population increase, indicating no strong interaction with the STH.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"17 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140635568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By means of density functional theory, the energy‐loss near‐edge structure (ELNES) of carbon K‐edge of Mo2TiAlC2 and corresponding MoTiC2 Mxene at orientational‐independent condition is dealt with. Compared to the MAX (M is transition metal, A is an elment from group 13–16, X is C or N) phase, the energy separations increase between the main spectral features at the C K edge of Mo2TiC2 MXene owing to the structural change and decreased bond length. The dispersions of the C K edge in both systems are similar to p‐symmetry densities of states. It is indicated that the source of the first fine structure at the C 1s edge in both phases mainly comes from the electron transfer to px + py‐like character. The other fine structures result from the transition to hybridization of pz and px + py states with the prominent contribution of px + py‐like character. Moreover, the comparison of C K‐edge ELNES spectra in three Mo‐based compounds reveals that, ongoing from Mo2TiAlC2 to Mo2TiC2 and then to Mo2C, the energy position of the fine structures is shifted to higher energies (blueshifted), due to the quantum confinement effects and the change of the chemical environment around the excited carbon.
通过密度泛函理论，研究了取向无关条件下 Mo2TiAlC2 和相应 MoTiC2 Mxene 碳 K 边的能量损失近边结构（ELNES）。与 MAX 相（M 为过渡金属，A 为 13-16 族中的一个元素，X 为 C 或 N）相比，由于结构的变化和键长的减少，Mo2TiC2 MXene 的 C K 边主要光谱特征之间的能级差距增大。这两种体系中 C K 边缘的分散与 p 对称态密度相似。研究表明，这两种物相中 C 1s 边缘第一个精细结构的来源主要是电子转移到 px + py 样性。其他精细结构来自 pz 和 px + py 状态的杂化转变，其中 px + py 样性的贡献突出。此外，通过比较三种钼基化合物的 C K 边 ELNES 光谱发现，在从 Mo2TiAlC2 到 Mo2TiC2 再到 Mo2C 的过程中，由于量子约束效应和激发碳周围化学环境的变化，精细结构的能量位置向更高能量移动（蓝移）。
{"title":"Theoretical Study of Carbon K‐Edge Energy‐Loss Near‐Edge Structure Spectra in the Ordered Mo2TiAlC2 MAX and Mo2TiC2 MXene","authors":"Zahra Derikvandi, Mehrdad Dadsetani","doi":"10.1002/pssb.202400012","DOIUrl":"https://doi.org/10.1002/pssb.202400012","url":null,"abstract":"By means of density functional theory, the energy‐loss near‐edge structure (ELNES) of carbon K‐edge of Mo2TiAlC<jats:sub>2</jats:sub> and corresponding MoTiC<jats:sub>2</jats:sub> Mxene at orientational‐independent condition is dealt with. Compared to the MAX (M is transition metal, A is an elment from group 13–16, X is C or N) phase, the energy separations increase between the main spectral features at the C K edge of Mo<jats:sub>2</jats:sub>TiC<jats:sub>2</jats:sub> MXene owing to the structural change and decreased bond length. The dispersions of the C K edge in both systems are similar to p‐symmetry densities of states. It is indicated that the source of the first fine structure at the C 1<jats:italic>s</jats:italic> edge in both phases mainly comes from the electron transfer to <jats:italic>p</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> + <jats:italic>p</jats:italic><jats:sub><jats:italic>y</jats:italic></jats:sub>‐like character. The other fine structures result from the transition to hybridization of <jats:italic>p</jats:italic><jats:sub><jats:italic>z</jats:italic></jats:sub> and <jats:italic>p</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> + <jats:italic>p</jats:italic><jats:sub><jats:italic>y</jats:italic></jats:sub> states with the prominent contribution of <jats:italic>p</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> + <jats:italic>p</jats:italic><jats:sub><jats:italic>y</jats:italic></jats:sub>‐like character. Moreover, the comparison of C K‐edge ELNES spectra in three Mo‐based compounds reveals that, ongoing from Mo<jats:sub>2</jats:sub>TiAlC<jats:sub>2</jats:sub> to Mo<jats:sub>2</jats:sub>TiC<jats:sub>2</jats:sub> and then to Mo<jats:sub>2</jats:sub>C, the energy position of the fine structures is shifted to higher energies (blueshifted), due to the quantum confinement effects and the change of the chemical environment around the excited carbon.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"39 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140635738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Debye temperature is a crucial parameter in understanding various properties of solids, including their melting temperature. This study focuses on 4H‐SiC, a material renowned for its wide bandgap and high thermal conductivity, making it ideal for high‐power electronic devices. Calculating various physical parameters for 4H‐SiC, including the Debye temperature, is crucial for semiconductor fabrication. However, it is observed that existing Debye models are unsuitable for computing the Debye temperature of 4H‐SiC. Therefore, phonon calculations alongside the Debye model to establish a new model for determining the Debye temperature of 4H‐SiC are used. This research has identified an optimal temperature range, referred to as the ‘T150’ model, between 150 and 160 K, which yields a Debye temperature consistent with experimental values. The newly developed “T150” model, demonstrated herein, holds the potential for determining the Debye temperatures of doped 4H‐SiC, other polytypes of 4H‐SiC, and other semiconductor materials, broadening its applicability in material science.
{"title":"New Debye Temperature Model of 4H‐SiC Crystal","authors":"Wei Jun Hsiung, Chih Shan Tan","doi":"10.1002/pssb.202400104","DOIUrl":"https://doi.org/10.1002/pssb.202400104","url":null,"abstract":"The Debye temperature is a crucial parameter in understanding various properties of solids, including their melting temperature. This study focuses on 4H‐SiC, a material renowned for its wide bandgap and high thermal conductivity, making it ideal for high‐power electronic devices. Calculating various physical parameters for 4H‐SiC, including the Debye temperature, is crucial for semiconductor fabrication. However, it is observed that existing Debye models are unsuitable for computing the Debye temperature of 4H‐SiC. Therefore, phonon calculations alongside the Debye model to establish a new model for determining the Debye temperature of 4H‐SiC are used. This research has identified an optimal temperature range, referred to as the ‘T150’ model, between 150 and 160 K, which yields a Debye temperature consistent with experimental values. The newly developed “T150” model, demonstrated herein, holds the potential for determining the Debye temperatures of doped 4H‐SiC, other polytypes of 4H‐SiC, and other semiconductor materials, broadening its applicability in material science.","PeriodicalId":20406,"journal":{"name":"Physica Status Solidi B-basic Solid State Physics","volume":"84 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140626720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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