Photoluminescence measurements in Ge-doped p-type Ga0.60Al0.40As

Abstract

Results of photoluminescence and Hall effect measurements of p-type Ge-doped Ga0.60Al0.40As grown by liquid phase epitaxy are reported. The effective segregation coefficient for Ge for growth at 785 °C is estimated to be ∼2×10−3. The photoluminescence spectra at 5.5 K are characterized by two edge emission bands at ∼1.91 and ∼1.88 eV and a broadband at ∼1.55 eV. The edge emission bands are identified to be donor-acceptor pair recombination bands involving the same donor but two different acceptors. The ionization energy of the donor is estimated to be 50–60 meV and the acceptor ionization energies are estimated to be ∼60 and ∼100 meV for the 1.91- and 1.88-eV bands, respectively. The deep acceptor is believed to involve a background impurity, most likely C or Si. It is suggested that the 1.55-eV band arises from a next-nearest neighbor complex consisting of Ge on an arsenic site and an As vacancy. Post-growth annealing treatment at 830 °C is found to decrease the photoluminescence intensity suggesting the presence of annealing induced nonradiative centers.