Effect of a GaAs buffer layer grown at low substrate temperatures on a high-electron-mobility modulation-doped two-dimensional electron gas

Abstract

Sidegating in GaAs integrated circuits can be eliminated in molecular beam epitaxially grown structure with the incorporation of a GaAs buffer layer grown at low substrate temperatures (200–300 °C). We have grown two films which were identical except one had the low-temperature buffer layer included in the film structure. The films were modulation-doped heterojunctions designed to produce a high-mobility two-dimensional electron gas. The electrical characteristics of the two-dimensional electron gas were identical for the two samples. No deleterious effect on the mobility or carrier density was observed with the incorporation of the low-temperature buffer layer. At 4.2 K both films exhibited carrier densities of 4×1011 cm−2 and mobilities of (1.4–1.7)×106 cm2/V s in the dark. After a brief illumination at 4.2 K, the samples exhibited carrier densities of 5×1011 cm−2 and mobilities of (1.6–2.0)×106 cm2/V s. These electron mobilities are comparable to the highest electron mobilities ever obtained at these electron densities.