The conduction-band discontinuity ΔEc of AlxGa1−xAs/In0.5Ga0.5P heterojunctions grown by liquid phase epitaxy on GaAs substrate was studied using the capacitance–voltage (C–V) characterization technique. The C–V measurements were made on a series of samples with x ranging from zero to about 0.3. The carrier profiles for the samples with x=0 and x=0.06 give ΔEc values of 90 and 40 meV, respectively, showing the type I (straddling) band line-up. For x=0.18 and 0.29, the values of ΔEc were 45 and 110 meV, respectively, with the carrier profile characteristic of the type II (staggered) band line-up. From these results, ΔEc of the heterojunction is found to vanish at about x = 0.12. This agrees well with our previous result determined from the photoluminescence measurements.

Photoluminescence properties of In0.5Ga0.5P/AlxGa1−xAs heterojunctions in both staggered and straddling band alignment regimes have been investigated. From the relation between the energies of below-band gap luminescence and Al compositions in the staggered band alignment regime, we determined the Al composition for null conduction band offset of the heterojunction as well as the conduction band offset value of In0.5Ga0.5P/GaAs heterojunction. Assuming the transitivity between the conduction band offset values, we also obtained the fraction of the band gap energy difference that is associated with the conduction band offset of an AlGaAs/GaAs heterojunction.

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 conduction-band discontinuity ΔEc and interface charge density σ have been studied for In0.5Ga0.5P/In1−xGaxAs1−yPy (y<0.3) heterojunctions prepared by liquid phase epitaxy. The carrier concentration profiles of both normal (In0.5Ga0.5P on In1−xGaxAs1−yPy) and inverted (In1−xGaxAs1−yPy on In0.5Ga0.5P) structures are obtained by capacitance–voltage measurements, which agree well with the results of the self-consistent numerical calculations. The current–voltage and deep-level transient spectroscopy measurements confirm the validity of the result. It is found that ΔEc corresponds to 18% of the band-gap difference ΔEg, for both normal and inverted structures.