Electron mobility in selectively Si-doped GaAs/N–Al0.3Ga0.7As quantum well heterostructures with super-flat interfaces grown on (411)A GaAs substrates by molecular beam epitaxy

Abstract

Reduced roughness of GaAs/Al0.3Ga0.7As heterointerfaces formed on (411)A substrates by Molecular Beam Epitaxy (MBE) was confirmed by measuring Two Dimensional Electron Gas (2DEG) mobility in selectively Si doped GaAs/N–Al0.3Ga0.7As Quantum Well (QW) structures with 4, 6, 8, or 50-nm thick GaAs wells. Below a QW thickness (Lw) of 8 nm, the 2DEG mobility at 15 K was mainly determined by interface roughness scattering and rapidly decreases with decreasing well thickness. The 2DEG in the (411)A selectively doped QW sample with Lw=4 nm has 34% higher mobility (μ=32 500 cm2/Vs) at 15 K than that of the (100) sample simultaneously grown (24 200 cm2/Vs). Every (411)A sample with Lw≤8 nm has 24–34% higher 2DEG mobility than the (100) sample simultaneously grown. This result indicates that smoother GaAs/Al0.3Ga0.7As interfaces were realized on the (411)A substrates. The (411)A sample with the 50-nm thick well shows 84% higher 2DEG mobility than the (100) sample simultaneously grown and its mobility is not determined by interface roughness scattering but ionized impurity scattering, which may suggest that MBE growth of GaAs and AlGaAs on the (411) GaAs substrates reduces unintentional impurity incorporation.