High mobility two-dimensional hole gas in an al_0.26ga _0.74as/gaas heterojunction

We have obtained two-dimensional hole gas with low temperature mobility as high as 3.8×105 cm2 V-1 s -1 at a density of 1×1011 cm-2. The sample was grown on (311)A orientation. We give arguments to show that (100) orientation is not the optimum orientation for the growth of high purity materials.