Optical and crystallographic properties and impurity incorporation of GaxIn1−xAs (0.44<x<0.49) grown by liquid phase epitaxy, vapor phase epitaxy, and metal organic chemical vapor deposition

Abstract

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.