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Stoichiometric mixtures of Ga and As powders were explosively shocked to create GaAs. The reactants were loaded into stainless steel capsules, which were, in turn, fitted into Sawaoka fixtures. The sample assemblies were struck with flyer plates traveling at 1.3 to 2.5 K m / s . The shocked samples were analyzed by specific gravity measurements, X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy (SEM). The density of the polycrystalline product ranged from 79 to 95 pct of theoretical. The XRD patterns showed only the presence of GaAs; however, small amounts of gallium-rich and arsenic-rich regions were found by energydispersive X-ray spectroscopy (EDS) analysis.

I.

INTRODUCTION

THE semiconductor industry is moving from silicon to gallium arsenide devices because the latter can operate at higher temperature and higher frequencies than the former. Unfortunately, GaAs devices are very expensive even though the reactant elements are not. Furthermore, GaAs is usually processed in an atmosphere of arsenic gas, and so, the resulting arsenic-rich material is an N-type semiconductor. Because the high cost of GaAs is due to processing, we wanted to develop a shock synthesis method by starting with the elements. The production of high-purity single crystals needed for semiconductors involves several steps. It was not expected that we could accomplish all of the processing steps with explosive processing. Rather, we wanted to develop a method that would be less expensive. Of course, GaAs produced by shock synthesis would be polycrystalline and, therefore, would require further processing by conventional means. Shock synthesis of compounds from the elements has been used successfully to create such materials as Ni3A1,111 TiAI3, t21 W C , TM and T i C . TM This technique is relatively inexpensive and therefore may be attractive for a material such as GaAs. Furthermore, with this approach, it is possible to change the elemental ratio of Ga to As when the reactant powders are mixed. By this means, either gallium-rich or arsenic-rich GaAs can be produced. That is, it is possible to produce either N-type or P-type GaAs. In addition, other elements such as aluminum can be added to the reactants. Chemical reaction between the Ga and As powders was induced by shock energy. An explosive was used to propel a steel flyer plate into a steel fixture containing elemental powder mixtures. Shock synthesis resulted in the formation of polycrystalline GaAs. While this form is not suitable for ordinary semiconductors, it can be used

ALAN R. MILLER, Professor of Metallurgy, is with the Metallurgy Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801. JEMMY HAO, Engineer, is with Procomp Systems Corporation, Houston, TX 77036. This paper is based on a presentation made in the symposium "Reaction Synthesis of Materials" presented during the TMS Annual Meeting, New Orleans, LA, February 17-21, 1991, under the auspices of the TMS Powder Metallurgy Committee. METALLURGICAL TRANSACTIONS A

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