METALLURGICAL ASPECTS OF GAAS-GE HETEROJUNCTIONS.
MASSACHUSETTS INST OF TECH CAMBRIDGE
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The structure of GaAs-Ge heterojunctions prepared by a back melting process was studied by X-ray diffraction, metallographic and electron micro-analyzer techniques. The boundary region between the GaAs and the Ge was found to consist of a four-layered band. A discontinuity between the two inner bands was brought about by solidification occurring simultaneously from the GaAs and the Ge side. The junction material on either side of the central discontinuity was found to have grown as a single crystal with the orientation of the parent substrate. It was found essential to determine the GaAs-Ge phase diagram. This was accomplished by a series of alloys containing 0 to 40 weight percent GaAs. Over this range the diagram is a simple eutectic with the eutectic point at 74 weight percent Ge and 845C. The limiting solubility of GaAs in Ge was found to be less than 5 weight percent. The Kossel divergent beam X-ray technique was used to study orientation relationships across the boundary layer. Author