Optical, crystallographic, and transport properties of nominally undoped n-type and Zn doped p-type Gax In1−xAs /InP (0.44<x<0.49) grown by liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), and metal organic chemical vapor deposition (MOCVD) have been studied and related to the different growth methods. Samples grown by LPE show in general much larger luminescence intensities than the VPE samples with similar impurity concentration and less structural and compositional inhomogeneities. Peaks related to free and bound excitons and to different impurities are found in the photoluminescence and absorption spectra of the undoped samples. The binding energy of the exciton is determined to be 2.1±0.1 meV, in agreement with hydrogenic theory. A longitudinal optical (LO) phonon energy of 32±0.5 meV is derived from LO-phonon replica of the exciton line. The dependence of the energy gap at T=2 K from the solid solution composition in the range xGa =45%–49% is determined yielding a bowing parameter of C=0.475 and a gap value of Eg =0.811 eV at optimum lattice match. Data on donor-acceptor pair transitions observed in the photoluminescence spectra are combined with secondary ion mass spectrometry data to identify for the first time different acceptors: C, Zn, and Si. Their binding energies are 13±1, 22±1, and 25±1 meV, respectively. C is the dominant acceptor in the MOCVD samples, but is hardly observable in the LPE and VPE samples. Si and Zn are present in LPE, VPE, and MOCVD samples. The Zn doped p-type samples show a broad donor-Zn-acceptor pair transition band accompanied by a weak LO-phonon replica and a very weak exciton line.

A model based on the exciton theory has been presented for lineshape analysis of photoreflectance (PR) spectra. Experimental PR spectra of high‐quality thick GaAs epilayers of different purity were measured to verify the theoretical results. It has been shown that excitonic effects completely prevail over the one‐electron theory in the formation of photoreflectance spectrum even at high electric fields and room temperature, giving evidence of the existence of Franz–Keldysh oscillations enhanced by excitonic effects. A comparison of PR spectra simulated using the exciton theory and the one‐electron approximation has shown that the semiperiods of the oscillations were practically similar. This demonstrates the validity of using the simple “high‐field” model of Aspnes and Studna to determine surface electric fields. In photoreflectance of thick ultrapure GaAs epilayers an oscillating structure was experimentally observed in the region between the excitonic and the fundamental bandgap. This provides a possibility for contactless characterization not only for doped (N ∼ 1014–1018 cm–3) but also for ultrapure (N ∼ 1011–1013 cm–3) GaAs epilayers as well as other semiconductor materials. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract. It is shown that effective mass approximation together with short range interface corrections can be used to calculate short-period abrupt (GaAs),/(AlAs), (001) superlattices. The results obtained are in excellent agreement with results of pseudopotential calculations (A. Zunger et al.) in a wide range of superlattices periods (from n = I to n = 20).

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