Field effect two-dimensional electron gases in modulation-doped InSb surface quantum wells

We report on transport characteristics of field effect two-dimensional electron gases in surface indium antimonide quantum wells. A 5 nm thin n-InSb capping layer is shown to promote the formation of reliable, low resistance Ohmic contacts to surface InSb quantum wells. High quality single-subband magnetotransport with clear quantized integer quantum Hall plateaus are observed to filling factor ν=1 in magnetic fields of up to B=18 T. We show that the electron density is gate-tunable, reproducible, and stable from pinch-off to 4×10¹¹ cm⁻², and peak mobilities exceed 24,000 cm²/Vs. Rashba spin-orbit coupling strengths up to 130 meV⋅Å are obtained through weak anti-localization measurements. An effective mass of 0.019m_e is determined from temperature-dependent magnetoresistance measurements. By comparing two heterostructures with and without a doping layer beneath the quantum well, we find that the carrier density is stable with time when doping in the ternary AlInSb barrier is not present. Finally, the effect of modulation doping on structural asymmetry between the two heterostructures is characterized.