Preparation of Ge/Si and Ge∕GaAs Heterojunctions

The effect of various substrate preparation techniques is investigated in the vapor growth of germanium on Ge, Si, and substrates. Important differences are noted for substrates which are iodine etched in situ, chemically etched, and cleaved in situ; namely, the appearance and crystal perfection of the overgrowth as well as epitaxial junction properties, all improve in the order of the above procedures. Flat, structureless overgrowths on cleaved substrates and growths with negligible stacking fault densities and dislocation densities of approximately 106 cm−2 on cleaved germanium substrates are obtained. However, strain and cracking of the overgrowth, in addition to higher defect densities occur in germanium grown on cleaved silicon substrates.

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