Valence-band discontinuities between InGaN and GaN were evaluated using the capacitance-voltage characteristics of p-InGaN/n-GaN heterojunction diodes with high hole concentrations in p-InGaN. This capacitance-voltage method is effective to evaluate valence-band discontinuities because the influence of the piezoelectric charges at the heterojunction is ignored due to high acceptor concentrations. The built-in potential obtained from the capacitance-voltage measurements decreased with the In mole fraction of p-InGaN. This result indicates that the valence-band discontinuity (ΔEv) increases with the In mole fraction (x) and is expressed as ΔEv (eV) = 0.85x for x ≤ 0.28. The ΔEv value obtained in this work is about 50% lower than that reported previously using the photoluminescence (PL) method.
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