Single-particle relaxation times in a pseudomorphic In0.7Ga0.3As/In0.52Al0.48As QW-HEMT structure with (411) A super-flat interfaces grown by MBE

Single-particle relaxation times in In0.7Ga0.3As/In0.52Al0.48As quantum well high electron mobility transistor (QW-HEMT) structures for two subbands (i = 0 and 1) are studied by fast Fourier transform analysis of Shubnikoov-de Haas (SdH) oscillations measured at 4 K in order to investigate remote impurity (RI) scattering in the QW-HEMT structure with effectively atomically flat interfaces over a wafer-size area ((4 1 1)A super-flat interfaces) grown on a (4 1 1)A InP substrate by molecular beam epitaxy. The (4 1 1)A QW-HEMT structure with thin spacer thickness of 3 rim shows two times longer single-particle relaxation times (tau(s)(0) = 0.71 X 10(-13) s and tau(s)(1) = 1.08 x 10(-13) s) compared to those (tau(s)(0) = 0.37 x 10(-13) s and tau(s)(1)=0.49 x 10(-13) s) for the corresponding QW-HEMT structure with conventional (100) interfaces, indicating that RI scattering is much reduced in the (4 1 1)A sample. Calculations of tau(s)(0) limited by RI scattering assuming random distribution of sheet-doped impurities show that the enhancement of tau(s)(0) for the (4 1 1)A QW-HEMT structure cannot be explained by laterally uniform spacer thickness resulting from the (4 1 1)A super-flat interfaces. Much reduced RI scattering in the (4 1 1)A QW-HEMT structure is considered to be mainly caused by extremely uniform distribution of sheet-doped impurities. (C) 2002 Elsevier Science B.V. All rights reserved.