Physics and applications of semiconductor heterostructures : I. Measurement of band offsets in semiconductor heterojunctions. II. Theoretical and experimental studies of tunneling in semiconductor heterostructure devices

Citation

Yu, Edward Tsu-Wei (1991) Physics and applications of semiconductor heterostructures : I. Measurement of band offsets in semiconductor heterojunctions. II. Theoretical and experimental studies of tunneling in semiconductor heterostructure devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/AXNV-8575. https://resolver.caltech.edu/CaltechETD:etd-08232007-120748

Abstract

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This thesis describes investigations concerning the physics and applications of band edge discontinuities in semiconductor heterojunctions. An historical overview and an assessment of the current experimental and theoretical understanding of band offsets are presented in Chapter 1. The physics and potential device applications of tunneling phenomena in semiconductor heterostructures are also introduced.

Part I of the thesis describes measurements of semiconductor heterojunction valence-band offsets by x-ray photoelectron spectroscopy (XPS). In Chapter 2, the basic physical principles of XPS are discussed, with emphasis on capabilities of the technique that are especially relevant in studies of semiconductor interfaces. The experimental procedures and data analysis techniques required to measure band offsets by XPS are also described. A measurement of the GaAs/AlAs (100) valence-band offset is presented in Chapter 3. Our results are discussed in the context of the recent controversy surrounding the value of the GaAs/AlAs band offset. The relationship between band offset commutativity and interfacial quality as elucidated by our experiments and by previously reported results is also explained. A measurement of the valence band offset for the lattice-mismatched Si/Ge (001) heterojunction system is described in Chapter 4. A method developed to extend the applicability of the XPS technique to the determination of strain-dependent band offsets is presented and applied to the Si/Ge (001) material system. Our results demonstrate the profound influence of strain on band offset values in lattice-mismatched heterojunctions. An interpolation scheme for determining band offset values for [...] alloy heterojunctions is described, and is used to demonstrate the consistency of our results with Si/[...] modulation doping experiments that have been reported. Studies of band offsets and interfacial reactions in III-V/II-VI heterojunction systems are reported in Chapter 5. Specifically, band offsets and interface chemistry have been examined in the A1Sb/GaSb/ZnTe material system; the influence of interfacial chemistry on band offset values is demonstrated, and implications of our work for the viability of proposed heterojunction approaches for fabricating visible light emitters are discussed. The measurement of the CdSe/ZnTe (100) valence band offset is described in Chapter 6. Our results are discussed in the context of possible heterojunction approaches for injection of electrons into p-ZnTe for fabricating visible light emitters, and implications of our results for the common anion rule are addressed.

Part II of the thesis describes theoretical and experimental studies of tunneling in semiconductor heterostructures. Various theoretical models we have used to simulate the electrical behavior of a wide variety of heterostructure devices are described in Chapter 7. These techniques are applied to the calculation of current-voltage characteristics for double-barrier tunnel structures proposed in the GaAs/ZnSe and InAs/ZnTe material systems. Theoretical and experimental studies of interband transport in the InAs/GaSb/AlSb material system are described in Chapter 8. Band alignments in the InAs/GaSb/AlSb system and material properties of InAs and GaSb are discussed in the context of both fundamental physics and device applications. Attention is then focused on a theoretical and experimental study of transport in the InAs/GaSb/InAs device structure that helped to clarify the basic nature of interband transport and the coupling between conduction-band and valence-band states in different layers of a heterostructure. In Chapter 9, a theoretical study of hole tunneling times in GaAs/AlAs double-barrier heterostructures is presented. The experimental observation of anomalously short hole tunneling times that motivated this work is reviewed, and a phenomenological model explaining this experimental observation as a consequence of valence-band-mixing is developed.

Thesis Files