In this work we address experimentally a number of unresolved issues related to microwave induced resistance oscillations (MIROs) leading to the zero-resistance states observed recently on 2D electron gases in $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ heterostructures. We stress the importance of the electrodynamic effects detected in both reflection and absorption experiments, although they are not revealed in transport experiments on very high mobility samples. We also study the exact waveform of MIROs and their damping due to temperature. A simple equation is given, which can be considered as phenomenological, which describes precisely the experimental MIROs waveform. The waveform depends only on a single parameter\char22{}the width of the Landau levels, which is related to the quantum lifetime. A very good correlation was found between the temperature dependencies of the quantum lifetime from MIROs and the transport scattering time from the electron mobility with a ratio ${\ensuremath{\tau}}_{\mathit{tr}}∕{\ensuremath{\tau}}_{q}\ensuremath{\simeq}20$. It is found that the prefactor in the equation for MIROs decays as $1∕{T}^{2}$ with the temperature which can be explained within the distribution function model suggested by Dmitriev et al. The results are compared with measurements of the Shubnikov\char21{}de Haas oscillations down to $30\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ on the same sample.

Microwave-induced resistance oscillations on a high-mobility two-dimensional electron gas: Exact waveform, absorption/reflection and temperature damping

A powerful method for mobility spectrum analysis is presented, based on Bryan’s maximum entropy algorithm. The Bayesian analysis central to Bryan’s algorithm ensures that we avoid overfitting of data, resulting in a physically reasonable solution. The algorithm is fast, and allows the analysis of large quantities of data, removing the bias of data selection inherent in all previous techniques. Existing mobility spectrum analysis systems are reviewed, and the performance of the Bryan’s algorithm mobility spectrum (BAMS) approach is demonstrated using synthetic data sets. Analysis of experimental data is briefly discussed. We find that BAMS performs well compared to existing mobility spectrum methods.

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Application of Bryan's algorithm to the mobility spectrum analysis of semiconductor devices

We study quantum and transport mobilities in a parabolic quantum-well structure when one or more subbands are occupied. We developed an original analytical method to extract the quantum mobility from the multiple occupied subband transport characteristics at low temperature. We tune the carrier density and hence the subband structure of the parabolic quantum well over a wide range by illumination with a red light-emitting diode. In order to obtain the quantum mobilities, Fourier transforms of the first differential of the experimental magnetoresistance traces (ρxx versus magnetic field) are taken and fitted by a conductivity tensor model in the same magnetic field range. We find that both the quantum and transport mobilities increase nonlinearly with increasing carrier density for both the first and second subbands and conclude that the intersubband scattering is predominantly large angle.

Quantum and transport mobilities in an AlGaAs∕GaAs parabolic quantum-well structure

http://absimage.aps.org/image/MAR05/MWS_MAR05-2004-002940.pdf

Quantum and transport mobilities in an AlGaAs/GaAs parabolic quantum well structure

Photoluminescence measurements at different temperatures have been performed to investigate the optical response of a two-dimensional electron gas in n-type wide parabolic quantum wells. A series of samples with different well widths in the range of 1000–3000A was analyzed. Many-body effects, usually observed in the recombination process of a two-dimensional electron gas, appear as a strong enhancement in the photoluminescence spectra at the Fermi level at low temperature only in the thinnest parabolic quantum wells. The suppression of the many-body effect in the thicker quantum wells was attributed to the decrease of the overlap between the wavefunctions of the photocreated holes and the two-dimensional electrons belonging to the highest occupied electron subband.

/pdf/many-body-effects-in-wide-parabolic-algaas-quantum-wells-2p7woxga60.pdf

Many-body effects in wide parabolic AlGaAs quantum wells

Classical magnetotransport coefficients were studied in a parabolic quantum well (PQW) structure with two subbands occupied which occupancies were determined using the Shubnikov - de Haas effect. Unexpectedly, a very low magnetoresistivity effect was observed in comparison with what was predicted from the classical point of view for a system with two kinds of carriers possessing high mobilities around 10-20 m2 V-1 s-1. It was shown that methods, including the mobility spectrum technique, based on multilayer approach were inconsistent to describe the magnetotransport in a PQW system because of a strong intersubband scattering. For analysis of the data, a theoretical approach was developed on the basis of solution of the Boltzmann kinetic equation and corresponding formulae were derived employing clearly understood physical parameters of intra- and intersubband scattering frequencies. Based on this theoretical approach the scattering frequencies were deduced from the experimental data. In the PQW the intersubband scattering was much stronger than the intrasubband scattering and it determined the main features of the magnetotransport coefficients.

Classical magnetotransport in a parabolic quantum well with a strong intersubband scattering

Transport properties of Si--doped InSb grown by molecular beam epitaxy are studied. The mobility spectrum (MS) analysis made over a wide temperature range reveals three species of carriers: those associated with the bulk of the film, and electrons in quantized subbands in the -layer. At low temperatures the MS data are consistent with self-consistent calculations and measurements of the Shubnikov - de Haas oscillations. The far-infrared cyclotron resonance lineshapes are well described by the Drude approximation using the obtained values of subband mobilities, concentrations and effective masses.

I A Panaev

Papers

Classical magnetotransport in a parabolic quantum well with a strong intersubband scattering

An investigation of the multicarrier transport properties of -doped InSb at high temperatures using a mobility spectrum technique