Photoluminescence of the In0.5Ga0.5P/AlxGa1−xAs heterojunction with Al mole fractions x=0.29 and x=0.19 is presented. Below-band-gap photoluminescence with a peak energy less than both band gap energies of the constituent materials was observed. As the laser excitation intensity was decreased, the peak energy of the luminescence shifted to the lower energy side and showed a saturation behavior. The full width at half maximum of the peak also decreased as the laser excitation intensity was decreased. These phenomena indicate that the heterojunction has a staggered band alignment at each value of the Al mole fractions. The expected band alignment of the heterojunction at various Al mole fractions is presented.

The conduction band discontinuity for n-N isotype In0.5Ga0.5P/Al0.43Ga0.57As heterostructure grown on (100) GaAs substrate by liquid phase epitaxy was measured by the capacitance-voltage profiling method. The composition of each ternary was determined by photoluminescence and double-crystal x-ray diffraction measurement. The measurement of conduction band discontinuity shows staggered band lineup with both bands of In0.5Ga0.5P above those of Al0.43Ga0.57As, and the calculated conduction-band discontinuity ΔEc and the fixed interface charge density σi are 157 meV and −3×1010 cm−2, respectively. The nonoptimized fabrication of the light emitting devices with AlGaAs/InGaP/AlGaAs double heterostructure can be explained by the staggered band lineup of In0.5Ga0.5P/AlxGa1−xAs heterointerface for x(AlAs)≳0.43.

The effect of oxygen on the electrical and optical properties of In0.5Ga0.5P epitaxial layers grown on (100) GaAs by liquid-phase epitaxy has been investigated by adding Ga2O3 to the growth melt. As the amount of Ga2O3 increases, the carrier concentration at 300 K decreases from 4×1016 to 4×1015 cm−3 and the Hall mobility at 77 K increases from 2400 to 4000 cm2/V s. The photoluminescence at 17 K shows that the peak intensity of an extrinsic transition in the In0.5Ga0.5P layer is reduced when Ga2O3 is added to the growth melt. These facts indicate that the main effect of Ga2O3 is the reduction of impurity concentration in the growth melt. In the In0.5Ga0.5P layer grown from the Ga2O3-added growth melt, the same deep trap, with an activation energy of 0.29 eV, as in an undoped layer is observed but the trap density is decreased. This implies that the deep trap is not due to a simple intrinsic defect, but related to an impurity.