Defect states with an occupation-dependent lattice configuration in zinc-doped Ga0.58In0.42P on GaAs

While lattice-matched Ga_0.51In_0.49P on GaAs has the ideal bandgap for the top converter in triple-junction GaAs-based solar cells, more complex designs will benefit from flexibility in the composition of this alloy. Changes in the gallium/indium ratio are accompanied by lattice-mismatch relative to GaAs substrates, so higher dislocation densities are expected in alternative gallium/indium epitaxial alloys. We report deep level transient spectroscopy (DLTS) and photocapacitance measurements on metamorphic, Zn-doped Ga_0.58In_0.42P. The experimental evidence, including thermally-activated non-exponential capture and escape and an augmented optical threshold energy, indicates that hole traps with an occupation-dependent lattice configuration are present in this device. Similar behavior has been linked with Zn-doping in GaAsP, raising the suspicion that zinc may also be involved in the AX-like complex reported here.