Lattice Dynamics and Semiconductor Physics

The following sections are included:

• PREFACE

• CONTENTS

During the academic year 1941-42 I was a senior in the Physics Department at the National Southwest Associated University in Kunming. The Department was quite small, with about 10 faculty members, 10 instructors, a few graduate students and not more than 20 students in each undergraduate class. When the academic year started in the fall of 1941, a new face appeared, auditing many of the senior and graduate courses and participating in all discussions. That was Huang Kun. He had already received his bachelor's degree in physics from Yenching University in Beiping, and had come to Kunming to join the Southwest Associated University as an instructor. Soon we got to know each other well, and that was the beginning of half of a century of warm friendship…

The following sections are included:

• INTRODUCTION

• ELECTRON-PHONON COUPLING REVEALED BY INFRARED SPECTROSCOPY
  • Dielectric Function
  • Analysis of Reflectivity Spectra
    • Electron-phonon coupling in small gap or zero gap semiconductors. HgTe
    • Electron-phonon coupling in layered insertion materials. In₂Se₃ and InSe

• ELECTRON-PHONON INTERACTION REVEALED BY LIGHT SCATTERING
  • Light Scattering on Single Excitations
  • Light Scattering by Plasmons
  • Observation of the Plasmon-Phonon Coupling by Light Scattering

• REFERENCES

The following sections are included:

• INTRODUCTION

• GROUND STATE ENERGY OF A SOLID
  • Density-functional theory
  • Electron-ion potential

• LATTICE DYNAMICS
  • Total energy difference method
  • Dielectric screening method
  • Polarizability matrix

• RESULTS
  • Phonon frequencies
  • Ground state properties
  • Electronic properties

• CONCLUSIONS

• ACKNOWLEDGMENT

• REFERENCES

The following sections are included:

• INTRODUCTION

• ENERGY LEVELS OF LOCALIZED POINT DEFECTS
  • Defect Wave Function Localization and Electron-Phonon Coupling - Extrinsic Self-Trapping
  • Metastable Defects (DX-centers)
    • Donors in CdF₂
    • DX centers in AlGaAs
    • Structural models of metastable defects
  • Many-Electron Phenomena
    • Problem of negative-U
    • Transition metal impurity levels

• DEFECT MEDIATED RECOMBINATION
  • Multiphonon Processes
  • Auger-type processes
    • Auger-type carrier trapping
    • Luminescence quenching by the Auger effect
  • Recombination enhanced defect reactions

• CONCLUDING REMARKS

• REFERENCES

In this paper we show how numerical simulations can provide non-perturbative results for static and dynamical properties of anharmonic crystals and crystal surfaces to all orders in the anharmonicity. Specifically, we use path integral quantum Monte Carlo methods to evaluate the thermodynamic functions of face centered cubic crystals, in which the atoms interact through the Lennard-Jones 6-12 potential, at low temperatures where quantum effects are important. The results are compared with the predictions of lattice dynamics in the harmonic approximation, and with the results of low order thermodynamic perturbation theory. From such comparisons we can determine the region in which quantum effects become important, when anharmonic effects become important, and the validity of low-order perturbation theory for the evaluation of these functions. We then calculate the frequency- and wave-vector-dependent spectral densities of the displacement correlation functions for atoms at the surface of a slab of argon and a slab of copper, both of which consist of twenty-one (001) layers. Results at two different temperatures are obtained by means of a molecular dynamics simulation of each of these systems. The atoms in the argon slab are taken to interact via the Lennard-Jones 6-12 potential. The atoms in the copper slab interact through a potential obtained by the embedded atom method. Anharmonic effects of all orders are taken into account in the molecular dynamics simulation of these slabs. The dispersion and lifetimes of the Rayleigh waves on the surfaces of the slab are determined at two different temperatures.

Polaritons describe the quanta of coupled photon-phonon modes in a crystal. This is an idea introduced by Prof. K. Huang¹ in 1950. Since then, thousands of papers have been written on the subject. It was well known that propagation of an electromagnetic wave in a medium near resonance is governed by anomalous dispersion, but treating the wave as an elementary excitation in the medium was a new and important concept. First, photons (can be extended outside a medium) and phonons (restricted to existing inside a medium) are now treated on equal footing. Second, the medium-dressed propagating electromagnetic modes are taken as characteristic modes of the medium. Third, the coupled mode idea can be extended to many other interesting problems in condensed matter physics…

The following sections are included:

• Introduction

• The Zero-Phonon Line and the Phonon Sidebands

• The Classical Limit and the Interaction node

• Quantal versus Classical Pictures

• References

When a bulk semiconductor with a direct gap is excited by an intense electromagnetic wave near the exciton resonance, the exciton polariton spectrum around the frequencies of Stokes and Anti-Stokes scattering will be mixed with certain phonons through the exciton-phonon interaction, producing new elementary excitations. These new elementary excitations are called “phonoritons”. In this paper the construction, existence condition, dispersion and other properties of the phonoriton are discussed. Two experiments for examination of the phonoriton spectrum reconstruction are proposed.

A quantum theory method is developed to study the surface Phonon-polaritons, with explicit inclusion of surface effects. The dispersion curve of surface phonon-polaritons is calculated, and a microscopic explaination is given for the experimental ATR data. It is found that the divergent nature of lights propagating along the fibers and waveguides is restrained.

The optical-phonon deformation potentials (ODP's) in tetrahedral semiconductors have been determined by the scalar relativistic linear Buffin-tin orbital method and atomic sphere approximation within density functional theory. It is shown that the ODP's can be directly calculated by adopting a frozen-phonon model without any adjustable Parameters. The effects of the empty sphere motion and the charge rearrangement on the ODP's are discussed. The wave-vector dependence of the ODP's on Λ-axis is also evaluated. The results Predict that the behaviours are possibly related to the symmetries of the band structure.

The following sections are included:

• Introduction

• Theory of capture by Multiphonon Emission (MPE)

• Negative U Center

• Extrinsic self-trapping phenomena

• Large lattice relaxation effects

• References

We report and summarize the results for the low frequency lattice vibration in semiconductors as induced by impurities, defects and crystalline-mixing which have been obtained in this laboratory and in the last few years. The defect and disorder activated transverse acoustic mode (DATA), the acoustic local mode, and the gap mode in some cases were observed, discovered and discussed.

The following sections are included:

• INTRODUCTION

• SOLITON AND POLARON DYNAMICS IN CONDUCTING POLYMERS
  • Ground State and Localized Excitations
  • Lattice Relaxation Approach for Dynamics
  • Some Results and Discussions

• HOLE MOTION IN A QUANTUM ANTIFERROMAGNET
  • The Model Hamiltonian
  • The Spin Relaxation Approach
  • Some Results and Comments

• ACKNOWLEDGEMENTS

• REFERENCES

The lattice vibration of the β -B_aB₂O₄ crystal have been analyzed with the aid of group theory. The Raman and infrared reflection spectra of this crystal have been investigated. Using a model of quasi-Layer molecular structure, the experimental results can be explained satisfactorily with an assignment of all internal and external vibrational modes.

A dipole lattice model proposed originally by Huang as applied to optical phonon modes in superlattices and quantum wells is reviewed, with emphasis on comparieon of boundary condition with the dielectric continuum model and linear chain model. Analytical expressions for the bulklike modes agreeing with the microscopic model have given support to the appropriate boundary condition, namely, both the displacement and potential should have nodes at the interfaces. Extention of the dipole lattice model to 1D quantum wires has demonstrated the characteristic of the optical phonon modes in 1D quantum systems for the first time.

Semiconductor surfaces and interfaces have been an active area of research for decades. The application of synchrotron radiation based spectroscopies have contributed significantly to the current understanding in this field. The principal focus of this paper is studies that have yielded insight into the nature of the atomic and electronic structure of semiconductor surfaces and interfaces. In addition, aspects of synchrotron radiation, measurement techniques and the MBE growth process are presented. Silicon is used as a prototypical covalent semiconductor, GaAs to illustrate some of the factors that become important when more chemical variation is introduced, and CaF₂ as a prototypical ionic insulator.

Superlattices and quantum wells have experienced tremendous growth in the last two decades. They have evolved to become a dominant subject in semiconductor physics, known as quantum heterostructures. On this occasion, we provide a perspective of their development with focus on major experimental observations.

The second order nonlinear susceptibility function χ⁽²⁾(ω) of the following five cubic semiconductors with a zinc-blend structure: GaAs, GaP, GaSb, InAs, and InSb are calculated following a band theoretical approach. Minimal basis semi-ab initio band structures for the five crystals which give correct experimental gaps are used. The calculation involves accurate integration of spectral function over the f.c.c. Brillouin zone with the dipole transition matrix elements fully taken into account. The present results are compared with other theoretical calculations. The calculated values for the zero frequency limit of χ⁽²⁾(ω) are in good agreement with a limited number of experimental data.

The current understanding of the optical transitions in very short period superlattices is briefly reviewed. Also reported are photoluminesence spectroscopic studies on a series of very short period (GaAs)_n-(AlAs)_n superlattice samples (n = 1, 2, 3 and 4) grown by molecular beam epitaxy. The results and discussions are mainly concerned with the ordering of the X_z and X_x,y valleys, the valley mixing induced by superlattice potential and interface potential, the excitation process and the phonon-assisted transitions.

The optical spectroscopy investigations of two-dimensional (2D) electron energy spectra in Si-MOSFET's and in GaAs- AlGaAs heterojunctions in the regimes of integral and fractional Quantum Hall Effect (QHE) are reviewed.

This paper gives a brief review of some recent experiments on the localization-delocalization transition in the integral quantum Hall effect and the new quantum liquid ground states giving rise to the fractional quantum Hall effect.

In this contribution I review some of the important results obtained on periodic and quasiperiodic composition al amorphous semiconductor multilayers made by rf glow discharge method in our laboratory. We show that most of the structures have sharp and smooth interfaces to better than 5 Ȧ. Emphasis is placed on evidence for quantum size effects in periodic heterostructures and on the striking features of the diffraction spectrum associated with the quasiperiodic structures.

The author gives a review on free exciton emission in MIS diodes with wide band gap II-VI compounds in forward bias. The research work includes as follows: Free exciton emission and its longitudinal optical (LO) phonon replicas in ZnSe and CdS MIS diodes have been identified in terms of Gross's theory. Pure green, blue, blue-violet and violet electroluminescence(EL) at room temperature(RT) have been obtained in II-VI compound MIS diodes, respectively. The origin of two blue EL bands at RT in ZnSe MIS diodes is attributed to emission related to free exciton. The homogeneity of blue EL in ZnSe MIS diodes has been improved by using a suitable insulating layer. Finally a new P band, which is ascribed to exciton-exciton(E_x-E_y) interaction has been found in ZnSe MIS diodes with high pulse current density.

The following sections are included:

• HETEROJUNCTION MODEL

• RESULTS AND DISCUSSIONS

• REFERENCE

• APPENDIX

The following sections are included:

• Introduction

• Electron-Atom System

• Force and Energy Balance Equations

• Weak Current Limit

• Conclusion

• References

The following sections are included:

• INTRODUCTION

• OPTICAL PROPERTIES OF AMORPHOUS SEMICONDUCTORS

• ION IMPLANTED SEMICONDUCTORS AND STRUCTURES OF MULTILAYERS

• INTERFACES BETWEEN METAL AND SEMICONDUCTORS

• THEORY OF INTERBAND SPECTRA AND DIMENSIONALITY

• REFERENCES

When I was a student in the department of physics, Peking University from 1952 to 1961, Prof.Kun Huang was one of the most respectivable teachers and scientists there. He has taught my classmates and me general physics, solid state physics and semiconductor physics one after another. All his lectures were so splendid as to give us very deep impression. When I became a graduated student, he was my supervisor. He has guided me to enter the gate of science and has been solicitous for my every step in the way. I wrote this review paper to offer my best congratulations to his seventieth birthday and wish him happiness and longevity.

The following sections are included:

• Introduction

• Formalism

• Some General Behavior of the Deep Impurity States

• Localized Modes of Phonons of Mass Defects

• Summary

• Acknowledgments

• REFERENCES

A brief description about the aspect of Ge/Si superlattices and their novel properties has been presented followed by a summary of our recent work on the fabrication of Ge/Si ultra-short period multi-layered structures by molecular beam epitaxy and some preliminary characterization by optical measurements.

A preliminary trial of enhancing the brightness or lowering the driving voltage of an electroluminescent cell is given. Based on the experimental facts that the most important and inevitable process in EL is the impact excitation or ionization, we attempt at enlarging the brightness by widening the impact excitation cross-section which is calculated and is found to be dependent on the energy distribution of impinging electrons¹).

Further we take into account the structure of conduction band and deduce a formula which shows the anisotrom of the impact cross-section²). Numerical calculations are performed and the results will be checked by experiments.

In order to overcome the loss in initial acceleration phase we preheat carriers and inject them into the high field acceleration zone, in which the production of streaming carriers is expected³). By this way we vary the energy distribution toward higher energy and really we observe the enhancement of brightness in several folds.

Magnetoresistances of two-dimensional holes in GaAs/p-Al_zGa_l-zAs heterostructures have been investigated in the context of particle-hole (p-h) Hartree interactions. Aplication of a magnetic field is to suppress the Hartree contribution between two different heavy holes, hh⁺ and hh⁻, and leads to an orbit-related magnetoresistence with a proper functional form and a positive sign in consistence with experiments.

The following sections are included:

• Introduction

• Experimental Details
  • Equipment
  • Preparation of atomically clean Si(100) surface
  • Experimental procedure

• Results and Analysis
  • The contaminations of C and O on Si(100) surface
  • Oxygen adsorption
  • Analysis of oxygen adsorption — the sticking coefficient S(θ)

• Discussion

• REFERENCES

Macroscopic dielectric theory provides a simple and widely used description of the principal long wavelength collective excitations of ionic or doped semiconductors. Recent experiments, however, show that the eigenvectors associated with standing wave normal modes of thin films produced by dielectric theory are qualitatively incorrect. This issue is reviewed, and recent theories which produce results in accord with the data are described.

It is well known that during the promulgation of the twelve Years plan for the development of science and technology in China in 1956, Professor Kun Huang played an important role both in designating semiconductor technology as one of the key priorities as well as in the further implementation of the plan. Since 1956, it is undeniable that semiconductor physics has become one of the most active branches in condensed matter physics in China in spite of the retardation of its progress due to the years of turmoil. The first National Conference of the Physics of Semiconductor (NCPS-1) was held in early sixties, since 1979 six NCPS were held every two years in succession. It is obvious that the development has been benefitted greatly through the policy of reform and opening up put forward near the end of 1978…

The following sections are included:

• Appendix: Scientific Publications of Prof K. Huang