D.L. Kirk

The growth of epitaxial ZnSe upon germanium substrates

Abstract This paper reports the growth conditions controlling the deposition by vacuum evaporation of epitaxial layers of n-type zinc selenide upon oriented p-type germanium substrates. The study has been performed in both conventional and ultra-high vacuum systems, with the growth proceeding from the vapour phase. The degree of ordering, growth rate and surface morphology of the zinc selenide layers has been systematically investigated as a function of the orientation and temperature of the germanium substrate and of the degree of residual vacuum in which the growth occurs. The influence that the source has in controlling epitaxy has also been observed. The growth techniques utilized in these studies are reported in detail and the underlying mechanisms controlling the growth process of ordered epitaxial layers are discussed.

Conditions of fabrication that control the interfacial microstructure of metal-semiconductor contacts formed from silver metal and (100)-oriented substrates of indium phosphide

Abstract An examination was made of the microstructure of silver contacts vacuum evaporated onto (100)-oriented substrates of indium phosphide. In the investigation we utilized the technique of X-ray diffractometry combined with a chemical profiling of the silver contact. The observations made with X-ray diffractometry were correlated with direct observation of the bulk silver and the metal- semiconductor interface by using scanning electron microscopy and element mapping. The influence of annealing conditions and chemical treatment of the substrate on the development of the bulk silver and the interfacial microstructure was also examined.

The nucleation and growth of zinc selenide onto (100) germanium surfaces

Abstract The present work reports on an assessment of the microstructure of layers of zinc selenide deposited from the vapour phase onto (100) germanium surfaces under conditions of ultrahigh vacuum (10 -10 −10 -9 torr). The structure of the continuous layers has been evaluated using transmission electron microscopy and X-ray diffractometry as a function of the temperature of the germanium substrate. The zinc selenide vapour being deposited has been characterized in terms of its state of dissociation and its incidence rate upon the germanium surface. At low substrate temperatures, polycrystalline deposits were obtained. These were dominated by the presence of included grains of both cubic sphalerite material with the (111) planes lying parallel to the (100) germanium surface and doubly positioned hexagonal wurtzite structures with their (00.1) basal plane parallel to the germanium surface. With increasing substrate temperature the layer become more highly ordered and the concentration of the included grains decreased. Discontinuous growth and the morphology of features of early growth have been observed with replica and extraction replica electron microscopy. These have been related to the structures occurring within the continuous deposits. Prior to deposition the structure and state of contamination of the germanium surface were evaluated with LEED (low energy electron diffraction), ESCA (electron spectroscopy and chemical analysis) and AES (Auger electron spectroscopy) techniques. Growth was found to be favoured on those germanium surfaces that had been stabilized with a monolayer coverage of oxygen. Without the presence of the oxygen, the germanium was chemically attacked by the Se 2 molecules present in the vapour beam. The nature and crystallography of the substrate surface structure have then been employed to help speculate on the primitive nucleation clusters that could have led to the observed morphology of the early growth features.

The effect of annealing treatment on the microstructure of layers of zinc selenide deposited onto (100) germanium surfaces

Abstract The present article describes a simple annealing treatment that achieves a dramatic improvement in the crystalline perfection of layers of zinc selenide deposited upon (100) germanium surfaces. The structure of the layers has been assessed with transmission electron microscopy and their microstructure is contrasted before and after this treatment.

The influence of ordered surface point defect arrays on the epitaxial deposition of gold upon (100) surfaces of sodium chloride

Abstract The effect of an ordered array of sodium ion vacancies (incorporated into a (100) surface of sodium chloride) upon the epitaxial temperature associated with gold being deposited onto that (100) surface has been investigated. A dramatic reduction in the epitaxial temperature has been observed, and single-crystal correctly oriented gold films have been achieved at - 30 °C upon those areas of the sodium chloride surface containing the point defects.

The influence of the method of deposition on the microstructure and optical properties of junctions of ZnSe with indium tin oxide

Abstract Junctions formed between optically active semiconductors and optically transparent conductors are finding increasing application in the design and development of opto-electronic devices. The preparation of junctions and interfaces with reproducible high quality optical transmission is a desirable objective. A detailed study has been made of the optical transmission and electrical conduction properties of junctions between ZnSe and indium tin oxide (ITO), a junction of considerable technological significance. The junctions were preared by the techniques of molecular beam epitaxy and r.f. sputter deposition. The conditions of fabrication that relate to the growth of a junction with high optical transmission, were established. Auger profiling showed that there is considerable chemical interaction between the ITO substate and the ZnSe during fabrication of the junction. For junctions prepared by sputter deposition, this activity can result in the deposition of high conductivity films of ZnSe.

The application of the capillarity model to the heterogeneous nucleation of zinc selenide upon (100) germanium surfaces

Abstract The present work tests experimentally the capillarity model of heterogeneous nucleation as applied to the nucleation of a binary semiconducting compound (zinc selenide) from a vapour phase of its dissociated components (Zn, Se2). It contrasts the experimentally observed pre-coalescence nucleation density, measured for differing substrate temperatures, with predictions from the model, the deposition being performed upon both clean restructured and oxygen-stabilized (100) germanium surfaces. The work also establishes under what conditions of a substrate surface the model is most likely to be applicable.

The nature of clean (100) surfaces of germanium

Abstract By using the techniques of Auger electron spectroscopy, photoelectron spectroscopy and low energy electron diffraction, the chemical state and structure of a clean (100) surface of germanium has been unambiguously resolved. Thermal annealing and argon ion sputtering are assessed as methods of reproducibly obtaining clean (100) germanium surfaces.