Smooth layers of epitaxial Ge have been grown on semi‐insulating GaAs using the pyrolysis of GeH 4 . Depositions were made between 600° and 850°C and the range most suitable for obtaining good growth was denned as 650°–750°C. Other factors affecting smoothness were substrate preparation, gas purity, and the total thickness of the deposit. The conductivity type profile of the deposits was determined using a traveling thermal probe on a beveled portion of the deposit, and it showed evidence of outdiffusion of both As and Ga from the substrate into the deposit in addition to As incorporation from the vapor phase. The semi‐insulating properties of the GaAs wafers were measured before and after depositions, and it was found that no degradation of the resistivity occurred if the substrates were treated in a 90 H 2 SO 4 : 5 H 2 O 2 : 5 H 2 O solution prior to depositions.
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Papazian et al. (1968) studied this question.