High-purity GaAs and Cr-doped GaAs epitaxial layers by MBE

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Abstract
Liquid‐nitrogen‐temperature Hall mobilities of about 105 000 cm2/V sec have been achieved in n‐type epitaxial layers grown by molecular beam epitaxy (MBE). The Hall mobility of the p‐type epitaxial layers at 78 °K was about 8440 cm2/V sec. The net donor concentration and the net acceptor concentrations for n‐type and p‐type epitaxial layers were about 4×1014 and 1×1014 cm−3, respectively. The compensation ratio in the n‐type epitaxial layers was about 0.4 as determined from the 78 °K electron mobility. Cr‐doped GaAs buffer layers for FET’s were grown in a substrate temperature range of 500–640 °C. Sheet resistances in excess of 109 Ω/ ⧠ were achieved when the substrate temperature during the growth was about 580 °C or higher. The amount of Cr that can be incorporated into the epitaxial layer showed a strong substrate temperature dependence.