Room temperature photoreflectance (PR) has been performed on three In0.32Ga0.68As/ In0.76Ga0.24As0.53P0.47 tensiley strained single-quantum-well structures, with heavy Zn modulation p-doping (5×1017 cm−3) in the quaternary barriers, which are lattice matched to an InP substrate. The PR spectra exhibit strong, well-defined, and regular Franz–Keldysh oscillations (FKO) associated with the barrier layers. We study the FKO in detail, comparing two different techniques of analyzing them to obtain a measure of the built-in electric field: (i) the conventional simple graphical asymptotic technique; and (ii) least-squares fitting to the experimental spectra using the recently proposed electromodulation model based on complex Airy functions. In the second method, the PR spectra are best described by the sum of two Airy function expressions representing degenerate heavy- and light-hole band edges. Good fits are obtained without the need to use an empirical energy-dependent broadening term to account for the effects of nonflatband modulation and nonuniform fields. The results are consistent with FKO originating from heavy- and light-hole transitions under the same electric field, but having a partial destructive interference effect in the PR spectrum. The fitted field value of ∼17 kV/cm is essentially the same as that obtained in the graphical analysis which assumed that the FKO were heavy-hole dominated. However, contrary to previous suggestions, neither the heavy- nor light-hole contributions dominate the actual FKO spectrum.

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The transport properties of Mg-doped, p-type GaN films grown by MOCVD have been measured using Hall effect and resistivity measurements over a temperature range of 400-120 K. The mobility is found to increase slowly over the temperature range of 400-150 K. Below this temperature the mobility is seen to decrease rapidly, while the corresponding Hall carrier density goes through a minimum before increasing to lower temperatures. These results have been analysed, using a two-band model. This incorporates a simple valence band model, calculated using a relaxation time approximation, and additional transport within an acceptor impurity band. A good fit has been obtained selfconsistently to both the mobility and carrier density over a temperature range of 400-120 K. We find that neutral scattering plays an important role in limiting the hole mobility.

The pressure dependence of the electron Hall mobility has been measured in a wide variety of InP and GaAs samples. The results, analyzed by a number of techniques, indicate that, in general, very good agreement can be obtained between theory and experiment for pure material at temperatures where ionized impurity scattering is unimportant. When heavily doped samples of liquid-phase epitaxy (LPE) GaAs and vapor-phase epitaxy (VPE) InP were measured it was not possible to predict the experimental pressure dependence of the mobility using the Brooks–Herring theory of scattering from ionized impurities. The possibility of inaccuracies in analysis have been reduced by using an iterative solution of the Boltzmann equation, phase shift calculations, and also Moore’s analysis [Phys. Rev. 160, 618 (1967)] for dressing and multi-ion corrections. However, these proved to be inadequate and we obtain the best agreement with experiment using the theory of Yanchev et al. [J. Phys. C 12, L765 (1979)] for scattering from a correlated distribution of impurities. The important effects of impurity correlation have been substantiated by studying samples of GaAs grown by molecular-beam epitaxy (MBE) and bulk GaAs subjected to neutron transmutation doping. The inability of impurities to correlate in such material is demonstrated by the close agreement between Brooks–Herring theory and experiment for these samples. When correlation scattering is taken into account, it becomes possible to explain the observed mobilities in heavily doped materials without having to always postulate autocompensation, as has been done by other authors.

Noncontact thickness and composition assessment of a strained AlGaAs/AlAs/InGaAs double barrier multiple quantum well structure Carrier mobilities in graded In x Ga1−x As/Al0.2Ga0.8As quantum wells for high electron mobility transistors