Abstract
We report magnetotransport measurements of InSb/Al1-xInxSb modulation doped quantum well (QW) structures and the extracted transport and quantum lifetime of carriers at low temperature We consider conventional transport lifetimes over a range of samples with different doping levels and carrier densities, and deduce different transport regimes dependent on QW state filling calculated from self-consistent Schrödinger–Poisson modelling. For samples where only the lowest QW subband is occupied at electron densities of cm−2 and cm−2 quantum lifetimes of ps, and ps are extracted from Shubnikov–de Haas oscillations below a magnetic field of T. The extracted ratios of transport to quantum lifetimes, and are similar to values reported in other binary QW two-dimensional electron gas systems, but are inconsistent with predictions from transport modelling which assumes that remote ionized donors are the dominant scattering mechanism. We find the low ratio and the variation in transport mobility with carrier density cannot be explained by reasonable levels of background impurities or well width fluctuations. Thus, there is at least one additional scattering mechanism unaccounted for, most likely arising from structural defects.
Highlights
We can approach the measured tt tq ratio in our model by increasing the interface roughness asperity parameter (D) and reducing the interface roughness lateral parameter (L), the input parameter values required in our model to fit the measured mobility, namely Nbkg = 1 ́ 1016 cm−3 and Δ = 6.5 ml, are already higher than expected when considering the measured value of background acceptors, Nbkg < 5 ́ 1014 cm−3 and such quantum well (QW) width fluctuations have not been previously observed in high resolution transmission electron microscope images of the InSb QW
Due to the low effective mass of InSb, the electron quantum lifetime of carriers in InSb/InxAl1-xSb QW structures can be extracted from magnetotransport measurements at very low magnetic field (B < 0.8 T) without the need for millikelvin sample temperatures
The SdH oscillations observed in the longitudinal magnetoresistance are associated with the QW 2DEG and are still discernible at fields as low as B = 0.4 T despite modest mobility extracted from Hall analysis
Summary
These properties make InSb suited to certain electronic applications and has allowed for the development of low voltage millimetre-wave transistors in comparison to more conventional gallium arsenide (GaAs) and indium phosphide (InP) based devices. The strong spin–orbit interaction and extremely large Landé g-factor (g » -50) [1, 7, 8] exhibited in InSb has gained attention for potential exploitation in spintronics and quantum information control [9,10,11] In such applications, the transport lifetime (tt) and electron quantum lifetime (tq), are useful figures of merit, where the latter is a measure of the mean lifetime of electrons in cyclotronic motion between momentum scattering events. We extract the electron transport and quantum lifetimes of carriers at low temperature (£2 K) and examine the extracted ratio of transport to quantum lifetimes, tt tq, with comparison to theoretically calculated values from selfconsistent Schrödinger–Poisson and transport modelling
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