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

Abstract

We report on transport characteristics of field effect two-dimensional electron gases (2DEGs) in surface indium antimonide quantum wells. The topmost 5 nm of the 30 nm wide quantum well is doped and shown to promote the formation of reliable, low resistance Ohmic contacts to surface InSb 2DEGs. High quality single-subband magnetotransport with clear quantized integer quantum Hall plateaus is 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 [Formula: see text] cm−2, and peak mobilities exceed 24 000 cm2/V s. Large Rashba spin–orbit coefficients up to 110 meV [Formula: see text]Å are obtained through weak anti-localization measurements. An effective mass of 0.019 me is determined from temperature-dependent magnetoresistance measurements, and a g-factor of 41 at a density of 3.6 [Formula: see text] cm−2 is obtained from coincidence measurements in tilted magnetic fields. By comparing two heterostructures with and without a delta-doped layer beneath the quantum well, we find that the carrier density is stable with time when doping in the ternary Al0.1In0.9Sb barrier is not present. Finally, the effect of modulation doping on structural asymmetry between the two heterostructures is characterized.

Quantum transport in InSb quantum well devices: progress and perspective

“…The dependence of the g-factor on the spin polarization P is of the most interest. Here, P can be calculated as P = r/ν, where ν is the filling factor [45,50,51,55]. In the regime where P is small, the g-factor closely agrees with k • p theory calculations.…”

“…Additionally, as reported by Bergeron et al [50], the instability of the InSb QWs could also be related to the Al in the upper barrier of InAlSb. According to this, the surface InSb QW is more stable than the QW with an InAlSb top barrier.…”

“…When P is much larger, the g-factor is enhanced by exchange interactions. Interestingly, in the density regime of the reported measurements , the effective gfactor also increases with carrier density, and the enhancement of the g-factor becomes more pronounced at higher carrier densities [45,50]. This observation is the opposite of what is known in the diluted 2DEG of GaAs [56].…”

“…For example, the channel that has been pinched off with a top gate will turn conductive again within minutes. This issue has been reported in many groups with independent growth and micro/nano fabrication processes [47,49,50]. Solving this issue requires optimization from both the MBE growth and the device fabrication.…”

“…In the undoped InSb QWs, where the asymmetry of the wave function can be enhanced with applied electric field, α SO is tuned by the top gate voltage [45,48]. Recently, in the work by Bergeron et al [50], a larger SOI has been reported in a surface InSb QW. Because of an even stronger asymmetry in the growth direction, α SO is measured to be as large as 110 meVÅ.…”