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.
Hole capture into and emission from self-organized InGaAs∕GaAs quantum dots (QDs) are studied by means of charge-selective deep level transient spectroscopy. The authors observe hole capture and determine activation energies and apparent capture cross sections for emission and capture. The experimental findings indicate that the capture process into the QDs in the presence of an applied electric field is controlled by phonon-assisted tunneling. An apparent capture cross section (at infinite values of temperature T and electric field F) σF,T=∞≈7×10−12cm2 and an average time tc≈0.3ps (T=300K) for hole capture and relaxation are obtained.
The results of measurements and numerical simulation of charge carrier distribution and energy states in strained quantum wells InxGa1−xAs/GaAs (0.06 x 0.29) by C-V-profiling are presented. Precise values of conduction band offsets for these pseudomorphic QWs have been obtained by means of self-consistent solution of Schrödinger and Poisson equations and following fitting to experimental data. For the conduction band offsets in strained InxGa1−xAs/GaAs -QWs the expression ∆EC(x) = 0.814x − 0.21x 2 has been obtained.
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