PHOTOLUMINESCENCE OF HEAVILY ZN-DOPED GA0.85IN0.15AS GROWN BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY

Zn-doped, p-type, Ga0.85In0.15As samples grown by low-pressure metalorganic vapor phase epitaxy, with free carrier concentrations in the range of 3.22 X 10(15) - 1.95 X 10(20) cm-3, have been studied by photoluminescence as a function of temperature. At low doping levels, recombinations involving discrete impurity states and free excitons provided a measurement of both the 0 K reference band gap, E(g)(0) = (1.296 +/- 0.003) eV, and of the Zn acceptor binding energy, E(Zn0) = (25 +/- 3) meV in the Ga0.85In0.15As alloy. High doping concentrations cause a band gap shrinkage \DELTAE(g)\ which has been observed with photoluminescence experiments. A model taking into account Kane band tails and assuming a constant matrix element for the relevant optical transitions has been fitted to the photoluminescence spectra of layers with doping levels in the range of 1.6 X 10(19) - 1.95 X 10(20) cm-3. This provided a good description of the experimental results. The 0 K band gap shrinkage, which appeared to be smaller than in GaAs, follows the relation \DELTAE(g)\ = 1.4 X 10(-8)p1/3 for Ga0.85In0.15As, with \DELTAE(g)\ in eV and p in cm-3.