Interface roughness characterization by electron mobility of pseudomorphic In0.74Ga0.26As∕In0.52Al0.48As modulation-doped quantum wells grown on (411)A InP substrates by molecular beam epitaxy

Abstract

Interface roughness of pseudomorphic In0.74Ga0.26As∕In0.52Al0.48As modulation-doped quantum wells (MD-QWs) grown on the (411)A and (100) InP substrates by molecular beam epitaxy was characterized by sheet electron concentration (Ns) dependence of two-dimensional electron gas (2DEG) mobility by applying gate bias at 15K. The (411)A MD-QW with well width of 4nm (8nm) showed value of 1.8–2.1 (1.5–1.6) times higher 2DEG mobility at 15K comparing to the corresponding (100) sample in the range of Ns (1.2–2.3×1012cm−2), which results from reduced interface roughness scattering due to the super-flat (411)A InGaAs∕InAlAs interfaces. By analyzing Ns dependence of the 2DEG mobility, we deduced wave-number dependence of the Fourier components of the lateral well-width fluctuation (Δq0) arising from the interface roughness in the range of q0=0.55–0.7nm−1. Values of ∣Δq0∣2 of the (411)A InGaAs∕InAlAs interface were about half of those of the (100) interface in the whole range of q0=0.55–0.7nm−1.