Electroreflectance and Photoluminescence Studies of In1-xGaxP1-yAsy Lattice-Matched to GaAs

Electroreflectance measurements were performed on In1-xGaxP1-yAsy quaternary alloys grown on (100) GaAs by liquid-phase epitaxy in order to determine the precise band gap (E0) and broadening parameter (Γ). It was found that the band gap energies obtained by photoluminescence measurements differ slightly from the precise energy gap determined by ER measurements. The broadening parameters in the ER spectra of In1-xGaxP0.7As0.3 LPE layers inside the miscibility gap of this alloy system are comparable with those of In1-xGaxP0.96As0.04 LPE layers, and hence the LPE growth is less affected by the immiscibility, suggesting that the extraordinarily broadened band-edge luminescence in In1-xGaxP0.7As0.3 is not due to the local distribution of the energy gap caused by the immiscibility. The effects of the immiscibility on the ER spectra are discussed in connection with the LPE growth conditions.