Our understanding of elementary carrier scattering processes in semiconductors on the femtosecond timescale has advanced remarkably in the past few years. Improvements in femtosecond optical pulse generation and detection techniques have allowed us to probe on shorter timescales with better sensitivity at carrier densities where complicated many-body interactions are manifest. We describe experiments in which non-thermal distributions of carriers are excited and studied in GaAs quantum wells. By modulation-doping, we introduce excess carrier populations which are thermalized to the lattice and study the effects of excess populations of electrons and holes alternately on the femtosecond thermalization. We obtain information on the effects of excess populations on inelastic carrier-carrier scattering rates, bandgap renormalization and electron-phonon coupling.
{"title":"Femtosecond Spectroscopy of Non-thermal Carrier Distributions in GaAs Quantum Wells","authors":"W. Knox","doi":"10.1364/qwoe.1989.mb1","DOIUrl":"https://doi.org/10.1364/qwoe.1989.mb1","url":null,"abstract":"Our understanding of elementary carrier scattering processes in semiconductors on the femtosecond timescale has advanced remarkably in the past few years. Improvements in femtosecond optical pulse generation and detection techniques have allowed us to probe on shorter timescales with better sensitivity at carrier densities where complicated many-body interactions are manifest. We describe experiments in which non-thermal distributions of carriers are excited and studied in GaAs quantum wells. By modulation-doping, we introduce excess carrier populations which are thermalized to the lattice and study the effects of excess populations of electrons and holes alternately on the femtosecond thermalization. We obtain information on the effects of excess populations on inelastic carrier-carrier scattering rates, bandgap renormalization and electron-phonon coupling.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130135911","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}
Advances in crystal growth technology have led to increased control of the crystal composition during the growth process. An example of this is the monolayer precision with which the composition of semiconductor crystals can be varied using molecular beam epitaxy (MBE). Since MBE growth on planar substrates affords control of the composition only along the growth axis, additional processing is required to introduce lateral variation of the crystal properties. The use of nonplanar substrates produces lateral variations in the properties of crystalline layers grown by MBE, adding a new dimension to the power of MBE as a tool for device fabrication.1–4 For example, growth on nonplanar substrates has been used for the fabrication of buried heterostructure quantum well lasers in a single growth step3, and it has been proposed as a technique for the fabrication of quantum wire lasers.3,4
{"title":"Orientation dependence of the aluminum concentration in AlxGa1−xAs epilayers grown by molecular beam epitaxy on a nonplanar substrate","authors":"M. Hoenk, H. Chen, A. Yariv, H. Morkoç, K. Vahala","doi":"10.1364/qwoe.1989.wa5","DOIUrl":"https://doi.org/10.1364/qwoe.1989.wa5","url":null,"abstract":"Advances in crystal growth technology have led to increased control of the crystal composition during the growth process. An example of this is the monolayer precision with which the composition of semiconductor crystals can be varied using molecular beam epitaxy (MBE). Since MBE growth on planar substrates affords control of the composition only along the growth axis, additional processing is required to introduce lateral variation of the crystal properties. The use of nonplanar substrates produces lateral variations in the properties of crystalline layers grown by MBE, adding a new dimension to the power of MBE as a tool for device fabrication.1–4 For example, growth on nonplanar substrates has been used for the fabrication of buried heterostructure quantum well lasers in a single growth step3, and it has been proposed as a technique for the fabrication of quantum wire lasers.3,4","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125802135","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}
K. Goossen, G. Boyd, J. Cunningham, W. Jan, DAB. Miller, D. Chemla, R. Lum
Recently there has been a maturing of the technology of GaAs/AlGaAs multiple quantum well (MQW) p -i (MQW)-n modulators1-4 and related self electro-optic effect (SEED) devices 5-7 grown on GaAs substrates by molecular beam epitaxy (MBE). It has been demonstrated that these devices can operate at several GHz8, and that with the incorporation of an MBE-grown dielectric mirror beneath the modulator they may operate in reflection mode.4 These properties make MQW modulators attractive as a device for communicating off chip via optical signals. Since the majority of electronic devices are silicon, it is important to determine the quality of GaAs MQW modulators grown on Si substrates.
近年来，利用分子束外延(MBE)在GaAs衬底上生长GaAs/AlGaAs多量子阱(MQW) p -i (MQW)-n调制器s1-4和相关的自电光效应(SEED)器件5-7的技术已经趋于成熟。已经证明，这些器件可以工作在几个GHz8，并且在调制器下面加入一个mbe生长的介电镜，它们可以在反射模式下工作这些特性使得MQW调制器作为一种通过光信号进行片外通信的设备具有吸引力。由于大多数电子器件都是硅材料，因此确定在硅衬底上生长的GaAs MQW调制器的质量是很重要的。
{"title":"Direct Experimental Comparison of GaAs-AlGaAs Multi-Quantum Well Modulators Grown on GaAs and Silicon Substrates","authors":"K. Goossen, G. Boyd, J. Cunningham, W. Jan, DAB. Miller, D. Chemla, R. Lum","doi":"10.1364/qwoe.1989.tub4","DOIUrl":"https://doi.org/10.1364/qwoe.1989.tub4","url":null,"abstract":"Recently there has been a maturing of the technology of GaAs/AlGaAs multiple quantum well (MQW) p -i (MQW)-n modulators1-4 and related self electro-optic effect (SEED) devices 5-7 grown on GaAs substrates by molecular beam epitaxy (MBE). It has been demonstrated that these devices can operate at several GHz8, and that with the incorporation of an MBE-grown dielectric mirror beneath the modulator they may operate in reflection mode.4 These properties make MQW modulators attractive as a device for communicating off chip via optical signals. Since the majority of electronic devices are silicon, it is important to determine the quality of GaAs MQW modulators grown on Si substrates.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127086358","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}
U. Koren, G. Eisenstein, R. Tucker, T. L. Koch, B. Miller
Photonic integrated circuits (PIC's) can be composed of many active waveguide elements such as lasers, detectors, optical modulators and switches, optical amplifiers etc. These elements can be optically coupled via a complex branching network of low loss passive waveguides all on the same semiconductor chip. Some of the more obvious advantages of this technology are the compact, stable and efficient couplings that can be obtained between the various optical elements of the PIC, and also the potential extensive use of optical amplifiers inside the PIC to compensate for undesirable optical losses that may occur inside the optical circuit or at the outside world. It is possible to use optical amplifiers as switching elements in combination with optical power combiners or splitters in a complex waveguide optical switching circuits. This opens the possibility of creating switching PIC's with switching speeds higher than 1 GHz and with inherent optical gain available in the actual switches.
{"title":"Integrated Multiple Quantum Well Lasers and Optical Amplifiers at 1.55 Micron Wavelength","authors":"U. Koren, G. Eisenstein, R. Tucker, T. L. Koch, B. Miller","doi":"10.1364/qwoe.1989.tuc2","DOIUrl":"https://doi.org/10.1364/qwoe.1989.tuc2","url":null,"abstract":"Photonic integrated circuits (PIC's) can be composed of many active waveguide elements such as lasers, detectors, optical modulators and switches, optical amplifiers etc. These elements can be optically coupled via a complex branching network of low loss passive waveguides all on the same semiconductor chip. Some of the more obvious advantages of this technology are the compact, stable and efficient couplings that can be obtained between the various optical elements of the PIC, and also the potential extensive use of optical amplifiers inside the PIC to compensate for undesirable optical losses that may occur inside the optical circuit or at the outside world. It is possible to use optical amplifiers as switching elements in combination with optical power combiners or splitters in a complex waveguide optical switching circuits. This opens the possibility of creating switching PIC's with switching speeds higher than 1 GHz and with inherent optical gain available in the actual switches.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129903212","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}
When electrons tunnel through a single barrier of AlAs between GaAs contact layers there is a possibility of transfer from the Γ-conduction band to the X-band.1,2,3 The basic mechanism for Γ-X transfer based on the model of Liu 3 is shown in Fig. 1 along with Γ (solid lines) and X (dashed lines) conduction-band profiles for a 5.2 nm AlAs barrier. A Γ-electron can (1) tunnel through the entire structure without transfer, it can (2) transfer to the X-minimum at the first interface and propagate through the AlAs layer before transferring back to the Γ-minimum, or it can (3) transfer to the X-minimum at the first interface and propagate through the whole structure. The transfer at the interfaces is described by an interaction vertex VΓX or a coupling parameter α as described in Ref. 3. The process (2) is relatively unimportant at low applied potentials but becomes dominant above about 0.3 V where the Fermi energy has crossed the X-band in the AlAs.
{"title":"Γ-X Transfer in Tunneling through Single AlAs Barriers","authors":"D. Landheer, H. Liu, M. Buchanan, R. Stoner","doi":"10.1364/qwoe.1989.tud2","DOIUrl":"https://doi.org/10.1364/qwoe.1989.tud2","url":null,"abstract":"When electrons tunnel through a single barrier of AlAs between GaAs contact layers there is a possibility of transfer from the Γ-conduction band to the X-band.1,2,3 The basic mechanism for Γ-X transfer based on the model of Liu 3 is shown in Fig. 1 along with Γ (solid lines) and X (dashed lines) conduction-band profiles for a 5.2 nm AlAs barrier. A Γ-electron can (1) tunnel through the entire structure without transfer, it can (2) transfer to the X-minimum at the first interface and propagate through the AlAs layer before transferring back to the Γ-minimum, or it can (3) transfer to the X-minimum at the first interface and propagate through the whole structure. The transfer at the interfaces is described by an interaction vertex VΓX or a coupling parameter α as described in Ref. 3. The process (2) is relatively unimportant at low applied potentials but becomes dominant above about 0.3 V where the Fermi energy has crossed the X-band in the AlAs.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127495796","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}
Transport physics, device performance (high responsivity, high detectivity, high speed, broad bandwidth) and potential advantages (over HgCdTe) of 10 μm GaAs/AlxGa1−xAs superlattice infrared detectors will be discussed.
{"title":"Quantum Well Intersubband Infrared Detectors","authors":"B. Levine","doi":"10.1364/qwoe.1989.wb1","DOIUrl":"https://doi.org/10.1364/qwoe.1989.wb1","url":null,"abstract":"Transport physics, device performance (high responsivity, high detectivity, high speed, broad bandwidth) and potential advantages (over HgCdTe) of 10 μm GaAs/AlxGa1−xAs superlattice infrared detectors will be discussed.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122619563","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}
Recently, excitonic optical nonlinearities in direct-gap-semiconductors have attracted much attention and have been studied extensively [1]. Of particular interest are the nonresonant excitonic nonlinearities for their potential applications to ultrafast all-optical devices. The nonlinear optical properties of exciton systems result, in general, from the deviation of excitons from non-interacting ideal bosons. Not only the mutual interaction between excitons, but also the anharmonic excitonphoton interaction, contribute to the excitonic optical nonlinearity. In this paper we develope a simple theory for nonresonant excitonic optical nonlinearity in two- and three-dimensional semiconductors, treating the above mentioned two kinds of anharmonicity on an equal basis.
{"title":"Excitonic Optical Nonlinearity in Two- and Three-Dimensional Semiconductors","authors":"T. Hiroshima","doi":"10.1364/qwoe.1989.tue1","DOIUrl":"https://doi.org/10.1364/qwoe.1989.tue1","url":null,"abstract":"Recently, excitonic optical nonlinearities in direct-gap-semiconductors have attracted much attention and have been studied extensively [1]. Of particular interest are the nonresonant excitonic nonlinearities for their potential applications to ultrafast all-optical devices. The nonlinear optical properties of exciton systems result, in general, from the deviation of excitons from non-interacting ideal bosons. Not only the mutual interaction between excitons, but also the anharmonic excitonphoton interaction, contribute to the excitonic optical nonlinearity. In this paper we develope a simple theory for nonresonant excitonic optical nonlinearity in two- and three-dimensional semiconductors, treating the above mentioned two kinds of anharmonicity on an equal basis.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128976360","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}
E. T. Heyen, M. Hagerott, A. Nurmikko, D. L. Partin
There have been a number of studies aimed at isolating radiative recombination in semiconductor quantum wells, a process which in many instances is strongly influenced by excitonic effects such as in III-V (e.g. GaAs [1]) or wide-gap II-VI (e.g. ZnSe [2]) semiconductor heterostructures. Recently, Matsusue and Sakaki have exploited modulation doped GaAs/(Ga,Al)As multiple quantum wells (MQW) to show how radiative recombination of a quasi-two dimensional (2D) free electron-hole gas can be distinctly identified while reducing excitonic complications [3]. In narrow-gap semiconductors, such as PbTe, excitonic effects are negligible; therefore quantum wells from these materials offer a clear opportunity to study quasi-2D free carrier radiative recombination over a wide temperature and density. We show here that radiative recombination dominates in high quality MBE-grown PbTe/(Pb,Eu)Te MQW’s. At the same time PbTe/(Pb,Eu)Te based heterostructures show excellent prospects as low threshold diode injection lasers at mid-infrared wavelengths [4].
{"title":"Free Carrier Radiative Recombination in 2D: PbTe Quantum Wells","authors":"E. T. Heyen, M. Hagerott, A. Nurmikko, D. L. Partin","doi":"10.1364/qwoe.1989.mc4","DOIUrl":"https://doi.org/10.1364/qwoe.1989.mc4","url":null,"abstract":"There have been a number of studies aimed at isolating radiative recombination in semiconductor quantum wells, a process which in many instances is strongly influenced by excitonic effects such as in III-V (e.g. GaAs [1]) or wide-gap II-VI (e.g. ZnSe [2]) semiconductor heterostructures. Recently, Matsusue and Sakaki have exploited modulation doped GaAs/(Ga,Al)As multiple quantum wells (MQW) to show how radiative recombination of a quasi-two dimensional (2D) free electron-hole gas can be distinctly identified while reducing excitonic complications [3]. In narrow-gap semiconductors, such as PbTe, excitonic effects are negligible; therefore quantum wells from these materials offer a clear opportunity to study quasi-2D free carrier radiative recombination over a wide temperature and density. We show here that radiative recombination dominates in high quality MBE-grown PbTe/(Pb,Eu)Te MQW’s. At the same time PbTe/(Pb,Eu)Te based heterostructures show excellent prospects as low threshold diode injection lasers at mid-infrared wavelengths [4].","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129922275","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}
R. Yan, R. Simes, H. Ribot, L. Coldren, A. Gossard
A field-dependent two-dimensional exciton due to a Van Hove type M1 singularity at the top of superlattice minibands has been observed in MBE grown superlattices for the first time at room temperature. The largest ever-reported room temperature two-dimensional heavy hole exciton shift up to ~30meV was observed by field-dependent photocurrent measurements.
{"title":"Van Hove Type M1 Exciton and Stark Localization Exciton in GaAs-AlGaAs Superlattices under an Electric Field","authors":"R. Yan, R. Simes, H. Ribot, L. Coldren, A. Gossard","doi":"10.1364/qwoe.1989.ma3","DOIUrl":"https://doi.org/10.1364/qwoe.1989.ma3","url":null,"abstract":"A field-dependent two-dimensional exciton due to a Van Hove type M1 singularity at the top of superlattice minibands has been observed in MBE grown superlattices for the first time at room temperature. The largest ever-reported room temperature two-dimensional heavy hole exciton shift up to ~30meV was observed by field-dependent photocurrent measurements.","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124172482","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. Zarem, P. Sercel, M. Hoenk, A. Yariv, K. Vahala
Submicron bandgap tailoring of semiconductors has many exciting applications such as optical waveguiding and carrier confinement. When the carriers are confined to dimensions comparable to their deBroglie wavelength, they exhibit quantum size effects [1,2,3]. Techniques such as molecular beam epitaxy of GaAs-AlGaAs structures allow for such tailoring in one dimension, but control in the other two dimensions requires other techniques. Most of the work toward lateral confinement of carriers to these dimensions has focused on etching techniques [1,3] due to the lack of other methods for creating such small structures. For most device applications, however, a lateral confining structure which does not create an exposed surface is essential. One such technique is the use of ion implantation to selectively disorder a quantum well [2].
{"title":"Disorder of a GaAs-AlGaAs Quantum Well as a Technique For Fabricating Quantum Wires","authors":"H. Zarem, P. Sercel, M. Hoenk, A. Yariv, K. Vahala","doi":"10.1364/qwoe.1989.tua5","DOIUrl":"https://doi.org/10.1364/qwoe.1989.tua5","url":null,"abstract":"Submicron bandgap tailoring of semiconductors has many exciting applications such as optical waveguiding and carrier confinement. When the carriers are confined to dimensions comparable to their deBroglie wavelength, they exhibit quantum size effects [1,2,3]. Techniques such as molecular beam epitaxy of GaAs-AlGaAs structures allow for such tailoring in one dimension, but control in the other two dimensions requires other techniques. Most of the work toward lateral confinement of carriers to these dimensions has focused on etching techniques [1,3] due to the lack of other methods for creating such small structures. For most device applications, however, a lateral confining structure which does not create an exposed surface is essential. One such technique is the use of ion implantation to selectively disorder a quantum well [2].","PeriodicalId":205579,"journal":{"name":"Quantum Wells for Optics and Optoelectronics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125790335","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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