The process of impurity‐induced layer disordering (IILD) or layer intermixing, in AlxGa1−xAs‐GaAs quantum well heterostructures (QWHs) and superlattices (SLs), and in related III‐V quantum well heterostructures, has developed extensively and is reviewed. A large variety of experimental data on IILD are discussed and provide newer information and further perspective on crystal self‐diffusion, impurity diffusion, and also the important defect mechanisms that control diffusion in AlxGa1−xAs‐GaAs, and in related III‐V semiconductors. Based on the behavior of Column III vacancies and Column III interstitials, models for the crystal self‐diffusion and impurity diffusion that describe IILD are reviewed and discussed. Because impurity‐induced layer disordering has proved to be an important method for III‐V quantum well heterostructure device fabrication, we also review the application of IILD to several different laser diode structures, as well as to passive waveguides. We mention that it may be possible to reali...

Atom diffusion and impurity‐induced layer disordering in quantum well III‐V semiconductor heterostructures

Recent developments in both GaAs- and InP-based opto-electronic circuits (OEIC's) which incorporate both optoelectronic and electronic devices on the same semiconductor substrates will be discussed. Several key technologies required for optoelectronic integration and the present status of the technology are explained by reviewing some of OEIC transmitters and receivers that have been realized up to now. Possibilities of application of OEIC's and further technological challenges to enhance the advantages of OEIC's are discussed.

Recent progress in optoelectric integrated circuits (OEIC's)

Recent experiments have shown that quantum well structures grown on a GaAs substrate can be destroyed by dopant diffusion. It is observed that existing models proposed to explain the phenomena are not in accordance with most available experimental results. We propose an alternative mechanism to explain the quantum well destruction phenomenon. The mechanism is based on the effect of the Fermi level on the concentrations of charged point defects which contribute to diffusion processes. This conceptually simple mechanism is consistent with most available experimental results on a qualitative basis. In this mechanism, the doping level and the doping type (p or n) are of primary importance, and not some other detailed atomistic nature of the dopant species. Furthermore, it is the presence of the dopant that is important, and not its motion, i.e., its diffusion.

Destruction mechanism of III‐V compound quantum well structures due to impurity diffusion

At the beginning we present a review of the historical development of first observations of domain structures in ferroelectric and ferroelastic crystals with a SEM. A theory of the charging mechanism of an insulating sample bombarded by an electron beam gives an interpretation of experimental observations of ferroelectric crystals. This model is studied in order to give a guide to accomplish experiments and to interpret the observations of domains. A model of formation of the contrast between ferroelectric domains is presented. Visualization of domains and results obtained with unmetallized ferroelectric and ferroelastic crystals (TGS, BaTiO3, GASH, PbHPO4, LAS, etc.) are presented. The influence of the temperature and some other parameters on the domain structures is studied and their modifications at the ferroelectric-ferroelastic and ferroelectric-paraelectric phase transitions are also mentioned. Results obtained by the scanning electron decoration technique (SEDT) are presented.

Study of ferroelectric and ferroelastic domain structures by scanning electron microscopy

Si-rich silicon nitride thin films have been deposited by low pressure chemical vapor deposition, at 850 °C from mixtures of dichlorosilane and ammonia. The films’ elastic properties have been studied as a function of film composition. Fourier transform infrared spectroscopy and ellipsometric data indicate that the local atomic strain is a strong function of the calculated volume fraction of Si contained in the films. A relationship is observed that shows the strain to be inversely proportional to the cube root of the Si volume fraction. A model that accounts for distortion in Si–SixN4−x tetrahedra (x=0–4), upon substitution of silicon for nitrogen in the film is applied to the data. The model is shown to be consistent with measurements of intrinsic film stress across a compositional range from stoichiometric silicon nitride, Si3N4, to nitrogen-free amorphous silicon, a-Si.

Stress relaxation in Si-rich silicon nitride thin films

Transverse mode controlled high power AlGaAs lasers with a window stripe buried multiquantum well structure have been developed using the simple and reliable Zn-diffusion-induced disordering process. The maximum pulsed light output of the laser is 240 mW. The lasers operate in a fundamental transverse mode up to 100 mW. The threshold current and external differential quantum efficiency depend on the total window region length, because of large free carrier absorption in the Zn diffused window region. By controlling the diffusion depth and window region length, the lasers with low threshold current and high external differential quantum efficiency are realized.

AlGaAs Window Stripe Buried Multiquantum Well Lasers

The reactive-ion etching (RIE) process in fabricating mirror facets for AlGaAs/GaAs buried multiquantum well (BM-QW) lasers has been developed. The lasers have a window structure where a mirror is formed by RIE. Window and BM-QW structures are fabricated by Zn-diffusion-induced disordering. Because of no carrier injection, the damage caused by RIE does not affect the characteristics of the lasers. The lasers having one facet formed by RIE and the other by cleaving operate in the fundamental transverse mode. A low threshold current (25 mA) and high external quantum efficiency are comparable to those of cleaved lasers.

AlGaAs/GaAs Buried Multiquantum Well Lasers with a Reactive Ion Etched Window Facet

Transverse mode stabilized AlGaAs/GaAs multiquantum well (MQW) lasers with buried MQW optical guide (MQW-BOG) have been fabricated utilizing Zn-diffusion-induced disordering of AlGaAs/GaAs MQW. Lasers with such an optical guide structure operate in the fundamental transverse mode up to an output power as high as 30 mW. A small kink is observed in the L-I curve at an output power exceeding 30 mW. Above the kink, a twin peak appears in the far-field pattern while a single peak appears in the near-field pattern. From these results, it is confirmed that the MQW-BOG laser acts as an index guided laser with partial gain-guided effect.

http://iopscience.iop.org/article/10.1143/JJAP.24.L548/pdf

AlGaAs/GaAs Multiquantum Well Lasers with Buried Multiquantum Well Optical Guide

Zn diffusion induced disordering of a GaAlAs-GaAs multiquantum-well (MQW) structure has been studied by cross sectional transmission electron microscopy. The disordering is found to occur uniformly along the lateral direction within a transition region of about 0.2 µm. The narrow width of the transition region is explained by the steep Zn concentration gradient of the diffusion front.

Cross Sectional Transmission Electron Microscopy of Zn Diffusion Induced Disordering of GaAlAs-GaAs Multiquantum-Well Structures

The influence of resist and absorber stress distributions on X-ray mask distortion induced during back-etching preceding subtractive fabrication is analyzed experimentally and simulated. The stress distribution (gradient) in a resist and/or that in an absorber film causes larger pattern displacement rather than the film average stress. Some resists have considerably high stress after coating on a wafer, and this stress also changes during exposure, causing local pattern displacements. However, use of chemically amplified resist systems, in which the reaction after exposure is limited to a small amount acid generation, might solve this problem. Low-stress positive-tone resists should thus be developed.

https://iopscience.iop.org/article/10.1143/JJAP.35.2845/pdf

Tsuneaki Ohta

Papers

AlGaAs Window Stripe Buried Multiquantum Well Lasers

AlGaAs/GaAs Buried Multiquantum Well Lasers with a Reactive Ion Etched Window Facet

AlGaAs/GaAs Multiquantum Well Lasers with Buried Multiquantum Well Optical Guide

Cross Sectional Transmission Electron Microscopy of Zn Diffusion Induced Disordering of GaAlAs-GaAs Multiquantum-Well Structures

X-ray mask distortion induced in back-etching preceding subtractive fabrication : Resist and absorber stress effect