D. Wuu, Shiau‐Yuan Huang, Shuo-Huang Yuan, R. Horng, S. Ou, Bo-Wen Shiao
Ultra-wide bandgap zinc gallium oxide (ZGO) and GO films were prepared on c-plane sapphire by conventional radio-frequency magnetron sputtering. In the current sputtered oxide studies, target composition or growth temperature is usually the main deposition variable, and the other growth conditions are fixed. This would make it difficult to fully understand the theory and characterization of ZGO films. In this study, several growth parameters as well as the post-thermal treatment were all modulated to realize and optimize the ZGO growth. From x-ray and TEM analyses, stabilization of stoichiometry and control of crystallinity transformation were confirmed to be important factors in determining the film quality. The optical bandgap of ZGO can reach 5.0-5.1 eV with a maximum responsivity peak at 240 nm. A metal-semiconductor-metal photodetector is demonstrated with a maximum responsivity over 2 A/W under a 5-V biased voltage. Furthermore, the photo/dark current ratio can be improved to be over ten thousand. As compared with those of the sputtered GO photodetector, the spectral response peak of ZGO showed a blue shift to 240 nm with higher responsivity. The data presented exhibit the ZGO material will become another potential candidate for ultra-wide bandgap semiconductor applications.
{"title":"Deposition and structure transformation of ultra-wide bandgap ZnGa2O4 materials (Conference Presentation)","authors":"D. Wuu, Shiau‐Yuan Huang, Shuo-Huang Yuan, R. Horng, S. Ou, Bo-Wen Shiao","doi":"10.1117/12.2511340","DOIUrl":"https://doi.org/10.1117/12.2511340","url":null,"abstract":"Ultra-wide bandgap zinc gallium oxide (ZGO) and GO films were prepared on c-plane sapphire by conventional radio-frequency magnetron sputtering. In the current sputtered oxide studies, target composition or growth temperature is usually the main deposition variable, and the other growth conditions are fixed. This would make it difficult to fully understand the theory and characterization of ZGO films. In this study, several growth parameters as well as the post-thermal treatment were all modulated to realize and optimize the ZGO growth. From x-ray and TEM analyses, stabilization of stoichiometry and control of crystallinity transformation were confirmed to be important factors in determining the film quality. The optical bandgap of ZGO can reach 5.0-5.1 eV with a maximum responsivity peak at 240 nm. A metal-semiconductor-metal photodetector is demonstrated with a maximum responsivity over 2 A/W under a 5-V biased voltage. Furthermore, the photo/dark current ratio can be improved to be over ten thousand. As compared with those of the sputtered GO photodetector, the spectral response peak of ZGO showed a blue shift to 240 nm with higher responsivity. The data presented exhibit the ZGO material will become another potential candidate for ultra-wide bandgap semiconductor applications.","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"2016 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114446365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With a high bandgap of 4.7 eV, β-Ga2O3 can be made semi-insulating by doping with Fe or Mg and thereby possesses a very high breakdown field necessary for high-powered switches. Somewhat surprisingly, β-Ga2O3 can also be made highly conductive by doping with Si, which leads to great potential for n+ohmic contacts and transparent current spreading layers. In the latter application, the goal is to achieve both high conductivity (high concentration n and mobility μ) and high transparency in the visible and UV regions. Recently we have achieved n = 2 x 1020 cm-3 in β-Ga2O3, using pulsed laser deposition (PLD) with a Ga2O3 target containing 1-wt%-SiO2. Although n is temperature-independent, µ is not, and by fitting µ vs T, we can determine donor ND and acceptor NA concentrations. However, at higher temperatures, µ is strongly affected by longitudinal optical (LO) phonon scattering, which is much more complicated to model in Ga2O3 (9 LO phonons) than in ZnO, GaN, and other binary semiconductors (1 LO phonon). Highly-doped samples have another complication, disorder in the dopant placement. Fortunately, this disorder leads to small quantum corrections delta sigma in the conductivity which are also affected by LO phonons. Indeed, the study of delta sigma vs T and vs magnetic field B at low temperatures is crucial in understanding mobility at 300 K. We demonstrate calculations of ND and NA in PLD-grown β-Ga2O3 under the assumption that the dominant acceptor is the Ga vacancy in various charge states.
{"title":"Using small low-temperature quantum effects to calculate 300-K mobility in complex degenerate semiconductors: Ga2O3 (Conference Presentation)","authors":"D. Look","doi":"10.1117/12.2516138","DOIUrl":"https://doi.org/10.1117/12.2516138","url":null,"abstract":"With a high bandgap of 4.7 eV, β-Ga2O3 can be made semi-insulating by doping with Fe or Mg and thereby possesses a very high breakdown field necessary for high-powered switches. Somewhat surprisingly, β-Ga2O3 can also be made highly conductive by doping with Si, which leads to great potential for n+ohmic contacts and transparent current spreading layers. In the latter application, the goal is to achieve both high conductivity (high concentration n and mobility μ) and high transparency in the visible and UV regions. Recently we have achieved n = 2 x 1020 cm-3 in β-Ga2O3, using pulsed laser deposition (PLD) with a Ga2O3 target containing 1-wt%-SiO2. Although n is temperature-independent, µ is not, and by fitting µ vs T, we can determine donor ND and acceptor NA concentrations. However, at higher temperatures, µ is strongly affected by longitudinal optical (LO) phonon scattering, which is much more complicated to model in Ga2O3 (9 LO phonons) than in ZnO, GaN, and other binary semiconductors (1 LO phonon). Highly-doped samples have another complication, disorder in the dopant placement. Fortunately, this disorder leads to small quantum corrections delta sigma in the conductivity which are also affected by LO phonons. Indeed, the study of delta sigma vs T and vs magnetic field B at low temperatures is crucial in understanding mobility at 300 K. We demonstrate calculations of ND and NA in PLD-grown β-Ga2O3 under the assumption that the dominant acceptor is the Ga vacancy in various charge states.","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133530819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Shining light on oxide-based nanostructures: tunable plasmonics and spintronics (Conference Presentation)","authors":"R. Serna, J. Toudert, A. Mariscal","doi":"10.1117/12.2511297","DOIUrl":"https://doi.org/10.1117/12.2511297","url":null,"abstract":"","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121391699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Inspection and functionality convergence (Conference Presentation)","authors":"Matthew C. Putman, V. Pinskiy, D. Sharoukhov","doi":"10.1117/12.2518129","DOIUrl":"https://doi.org/10.1117/12.2518129","url":null,"abstract":"","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114417105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Ton‐That, T. Huynh, L. L. Lem, A. Kuramata, M. Phillips
We used temperature-resolved cathodoluminescence to determine the characteristics of luminescence bands and carrier dynamics in edge-defined film-fed grown (EFG) beta-Ga2O3 single crystals synthesized by Tamura Corporation. The crystal is nominally undoped and has a (-201) surface orientation. The main impurities are Si, Ir, Al and Fe, with [Fe] ~ 10^17 cm-3 verified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The CL emission was found to be dominated by a broad UV emission peaked at 3.40 eV, which exhibits strong quenching with increasing temperature; however, its spectral shape and energy position remain virtually unchanged up to 500 K. Depth-resolved analysis reveals the luminescence spectrum is independent of sampling depth. We observed a super-linear increase of CL intensity with excitation density; this kinetics of carrier recombination can be explained in terms of carrier trapping and charge transfer at Fe3+/2+ centers. The temperature-dependent properties of this UV band were found to be consistent with weakly bound electrons in self-trapped excitons with an activation energy of 48 +/- 10 meV. In addition to the self-trapped exciton emission, a blue luminescence (BL) band is shown to be related to a donor-like defect, which increases significantly in concentration after remote hydrogen plasma treatment. The point defect responsible for the BL, likely an oxygen vacancy or a complex, is strongly coupled to the lattice with a Huang-Rhys factor S = 7.3.
{"title":"Kinetics of charge carrier recombination in beta-Ga2O3 single crystals (Conference Presentation)","authors":"C. Ton‐That, T. Huynh, L. L. Lem, A. Kuramata, M. Phillips","doi":"10.1117/12.2518229","DOIUrl":"https://doi.org/10.1117/12.2518229","url":null,"abstract":"We used temperature-resolved cathodoluminescence to determine the characteristics of luminescence bands and carrier dynamics in edge-defined film-fed grown (EFG) beta-Ga2O3 single crystals synthesized by Tamura Corporation. The crystal is nominally undoped and has a (-201) surface orientation. The main impurities are Si, Ir, Al and Fe, with [Fe] ~ 10^17 cm-3 verified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The CL emission was found to be dominated by a broad UV emission peaked at 3.40 eV, which exhibits strong quenching with increasing temperature; however, its spectral shape and energy position remain virtually unchanged up to 500 K. Depth-resolved analysis reveals the luminescence spectrum is independent of sampling depth. We observed a super-linear increase of CL intensity with excitation density; this kinetics of carrier recombination can be explained in terms of carrier trapping and charge transfer at Fe3+/2+ centers. The temperature-dependent properties of this UV band were found to be consistent with weakly bound electrons in self-trapped excitons with an activation energy of 48 +/- 10 meV. In addition to the self-trapped exciton emission, a blue luminescence (BL) band is shown to be related to a donor-like defect, which increases significantly in concentration after remote hydrogen plasma treatment. The point defect responsible for the BL, likely an oxygen vacancy or a complex, is strongly coupled to the lattice with a Huang-Rhys factor S = 7.3.","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130993293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Nasser, Doğuşcan Ahiboz, Ezgi Aygun, M. Borra, Ozan Akdemir, A. Bek, R. Turan
In this work, the electron-carrier-selectivity of ALD deposited TiO2 contact on n-type and p-type c-Si wafers is presented. The optical, compositional, and diode quality dependence of TiO2 on the ALD deposition temperature were analyzed using spectroscopic ellipsometry, AFM, XPS, GI-XRD, and CV measurements. By optimizing the ALD process parameters, an impressive effective minority carrier lifetime of up to 2.3 milliseconds corresponding to an iVoc of ~700 mV was obtained from wet chemical oxide-SiO2/TiO2 passivation stack layers. Finally, the asymmetry in C-V and J-V measurements betweenTiO2/n-type and TiO2/p-type c-Si heterojunctions was examined and the electron transport selectivity of TiO2 was revealed.
{"title":"Development of electron-selective SiO2/TiO2 stack layers with superior surface passivation capacity for n-type silicon substrates (Conference Presentation)","authors":"H. Nasser, Doğuşcan Ahiboz, Ezgi Aygun, M. Borra, Ozan Akdemir, A. Bek, R. Turan","doi":"10.1117/12.2510433","DOIUrl":"https://doi.org/10.1117/12.2510433","url":null,"abstract":"In this work, the electron-carrier-selectivity of ALD deposited TiO2 contact on n-type and p-type c-Si wafers is presented. The optical, compositional, and diode quality dependence of TiO2 on the ALD deposition temperature were analyzed using spectroscopic ellipsometry, AFM, XPS, GI-XRD, and CV measurements. By optimizing the ALD process parameters, an impressive effective minority carrier lifetime of up to 2.3 milliseconds corresponding to an iVoc of ~700 mV was obtained from wet chemical oxide-SiO2/TiO2 passivation stack layers. Finally, the asymmetry in C-V and J-V measurements betweenTiO2/n-type and TiO2/p-type c-Si heterojunctions was examined and the electron transport selectivity of TiO2 was revealed.","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123930076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Boltasseva, C. DeVault, V. Bruno, S. Saha, Z. Kudyshev, A. Dutta, S. Vezzoli, M. Ferrera, D. Faccio, V. Shalaev
Transparent Conducting Oxide (TCO) materials are degenerately-doped, wide-bandgap semiconductors which exhibit simultaneous high-conductivity and visible transparency. These unique properties are well known and frequently exploited for technologies such as touch-screen devices. In recent years, TCOs have been recognized as a promising material platform for nanophotonic devices, namely because of their simple, compatible fabrication, low-losses, dynamic modulation, and novel low-index properties. In this talk, I will highlight recent progress in the field of TCO-based nanophotonics, share our ongoing results and observations, and discuss future research challenges and directions. In particular, I will discuss our progress in developing metal-dielectric hybrid metasurfaces which incorporate TCOs for all-optical, ultrafast switching. Here, we incorporate defect-rich zinc oxide with a refractory titanium nitride metasurface for efficient light modulation at near-terahertz switching frequencies. My talk will also focus on TCO films for studying and observing low-index phenomena. Our recent work with aluminum-doped zinc oxide films demonstrates the ability for low-index materials to both enhance negative refraction and engender strongly coupled plasmonic systems with large room-temperature Rabi frequencies. Our work signifies the strong potential for incorporating transparent conducting oxides into plasmonic and nanophotonic devices to provide advances toward practical technologies and depth in scientific understanding.
{"title":"Through the (conducting) looking-glass: transparent conducting oxides for nanophotonic applications (Conference Presentation)","authors":"A. Boltasseva, C. DeVault, V. Bruno, S. Saha, Z. Kudyshev, A. Dutta, S. Vezzoli, M. Ferrera, D. Faccio, V. Shalaev","doi":"10.1117/12.2512275","DOIUrl":"https://doi.org/10.1117/12.2512275","url":null,"abstract":"Transparent Conducting Oxide (TCO) materials are degenerately-doped, wide-bandgap semiconductors which exhibit simultaneous high-conductivity and visible transparency. These unique properties are well known and frequently exploited for technologies such as touch-screen devices. In recent years, TCOs have been recognized as a promising material platform for nanophotonic devices, namely because of their simple, compatible fabrication, low-losses, dynamic modulation, and novel low-index properties. In this talk, I will highlight recent progress in the field of TCO-based nanophotonics, share our ongoing results and observations, and discuss future research challenges and directions. In particular, I will discuss our progress in developing metal-dielectric hybrid metasurfaces which incorporate TCOs for all-optical, ultrafast switching. Here, we incorporate defect-rich zinc oxide with a refractory titanium nitride metasurface for efficient light modulation at near-terahertz switching frequencies. My talk will also focus on TCO films for studying and observing low-index phenomena. Our recent work with aluminum-doped zinc oxide films demonstrates the ability for low-index materials to both enhance negative refraction and engender strongly coupled plasmonic systems with large room-temperature Rabi frequencies. Our work signifies the strong potential for incorporating transparent conducting oxides into plasmonic and nanophotonic devices to provide advances toward practical technologies and depth in scientific understanding.","PeriodicalId":106257,"journal":{"name":"Oxide-based Materials and Devices X","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124739334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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