HIGH-PURITY GAAS AND CR-DOPED GAAS EPITAXIAL LAYERS BY MBE

Liquid-nitrogen-temperature Hall mobilities of about 105 000 cm 2/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.