Short-range disorder effects on electronic transport in two-dimensional semiconductor structures

Abstract

We study theoretically the relative importance of short-range disorder in determining the lowtemperature 2D mobility in GaAs-based structures with respect to Coulomb disorder which is known to be the dominant disorder in semiconductor systems. We give results for unscreened and screened short-range disorder effects on 2D mobility in quantum wells and heterostructures, comparing with the results for Coulomb disorder and finding that the asymptotic high-density mobility is always limited by short-range disorder which, in general, becomes effectively stronger with increasing 'carrier density' in contrast to Coulomb disorder. We also predict an intriguing re-entrant metal-insulator transition at very high carrier densities in Si-MOSFETs driven by the short-range disorder associated with surface roughness scattering.One of the most spectacular applied physics and electronic materials advances of the last 40 years has been the 2000-fold enhancement of the low-temperature carrier mobility in molecular beam epitaxy (MBE)-grown GaAsbased 2D semiconductor structures. Between 1978, when the modulation doping technique was introduced by Störmer et al.1 in 2D n-GaAs-AlGaAs heterostructures, and now (i.e., 2014), the electronic mobility (µ) at low temperatures (below the Bloch-Grüneisen temperature scale, where phonons are unimportant 2 ) has increased in 2D GaAs systems from µ ≈ 2 × 10 4 cm 2 /Vs to µ ≈ 4 × 10 7 cm 2 /Vs 3 due to the steady improvement in purity, growth, fabrication, and processing techniques of individual 2D GaAs samples. As an aside, it may be pointed out that this increase in low-temperature mobility in 2D GaAs structures is comparable in magnitude to the much better known Moore's law exponential increase in the room-temperature microprocessor speed in CMOS devices achieved over the same time scale although the qualitative origins of the two enhancements are very different (better MBE growth and improved modulation doping for individual 2D n-GaAs structures whereas better packaging and miniaturization for Si microprocessors).In this work, we study theoretically the harmful effects of short-range disorder scattering in limiting the low-temperature electronic mobility in 2D GaAs structures, contrasting short-range disorder scattering with the corresponding long-range Coulomb disorder scattering arising from quenched charged impurities which has been extensively studied in the literature 4,5 . It is wellknown that Coulomb disorder arising from unintentional charged impurities in the background and from the intentional dopants needed in order to produce free carriers in semiconductors is the main mobility-limiting scattering mechanism in high-mobility 2D GaAs structures. However, at higher carrier densities, where Coulomb disorder is strongly screened out, other weaker and short-ranged scattering mechanisms arising from alloy disorder, interface roughness, neutral impurities, and defects could play a quantitative role in determining the 2D mobility in high-mobility 2D GaAs systems. Theoretically studying the ...

Electron and hole transport in disordered monolayerMoS2: Atomic vacancy induced short-range and Coulomb disorder scattering

“…[87]. However, as has been shown in numerous works [30,31,68,85,86], it is important to take into account screening for a correct description of the density and temperature dependence of the low-temperature conductivities in 2D systems.…”

“…II C 1 below. For scattering off the long-range Coulomb potential, we use the Born approximation which is justified due to the screening of the Coulomb potential [30,31,68,85,86]. For a degenerate 2DEG, the dielectric function is given by (q) = κ (1 + q TF /q), q < 2k F , where q TF = g s g v e 2 m * 4π 0 κh 2 is the Thomas-Fermi (TF) wave vector and κ is a background dielectric constant.…”

Quantum critical scaling for finite-temperature Mott-like metal-insulator crossover in few-layered MoS2

“…  predicted by the Mott-Ioffe-Regel theory 22 , where   is the spin and   the valley degeneracy:   = 2 and   = 6 for multilayer MoS 2 23 . Also, the resistivity maximum occurs at the temperature  * ~ 20 K much lower than the Fermi temperature   ~ 200 K. Very similar behavior of the resistivity has been reported in organic Mott systems 24 and only in particularly clean 2D systems 1,25 , and it has been interpreted to originate from strong correlation effects.…”

Recent experimental progress of fractional quantum Hall effect: 5/2 filling state and graphene

“…Scanning gate microscopy or scanning probes can serve as detectors for individual hard-scattering site and disorder potential [117][118][119]. A 2-impurity model (background and remote) was developed recently to address the relation between mobility, electron density, disorder and sample quality [120,121]. In addition to mobility and density, conditions for LED illumination, Aluminum fractions and silicon doping levels in heterostructure also affect the 5/2 FQH state [108,116].…”