Effects of piezoelectric fields on optoelectronic properties of InGaN/GaN quantum-well light-emitting diodes prepared on nonpolar (1 0 (1)over-bar 0) and semipolar (1 1 (2)over-bar 2) orientations

Optical and electrical characteristics of InGaN/GaN quantum-well (QW) light-emitting diodes (LEDs) are the subjects of this study. Samples were prepared on nonpolar (1 0 (1) over bar 0) and semipolar (1 1 (2) over bar 2) orientations of bulk GaN substrates. Electrical-bias-applied photoluminescence was employed as a characterization technique. It was confirmed that saturation of reverse photocurrent occurred around 0 V in nonpolar LEDs and at positive voltages in (1 1 (2) over bar 2)-oriented LEDs, while our previous study found negative voltages in (0 0 0 1)-oriented LEDs (Masui et al 2008 J. Phys. D: Appl. Phys. 41 165105). These results indicated that (1 1 (2) over bar 2)-oriented InGaN/GaN QWs experience piezoelectric fields being in the same direction as the built-in field. Piezoelectric field intensity was estimated to be -0.3 MV cm(-1) in the (1 1 (2) over bar 2)-oriented QW structure. Spectral comparison between photoluminescence and electroluminescence of the LED samples exhibited a tendency that spectral differences were insignificant in single-QW LEDs.