Combined Effect of Carrier Localization and Polarity in InxGa1-xN/GaN Quantum Wells.

The influence of carrier localization and polarization-induced electric fields on the spectral variation of photoluminescence was comparatively studied in polar and semipolar InxGa1-xN/GaN strained quantum wells embedded in p-i-n diodes. Two representative structures with x = 0.16 for polar (0001) diodes and potential fluctuations for semipolar diodes grown along (11 (2) over bar2) direction have been investigated with a reverse bias up to -4 V. From the s-shaped spectral shift as a function of temperature, the existence of single and triple localization traps was confirmed in polar and semipolar diodes. Within our bias range, we observed the monotonic blueshift with reverse bias in the polar sample, indicating that the carriers are laterally localized and thus influenced by the vertical piezoelectric fields. In clear contrast, the semipolar sample showed the blueshift of localized states only at low temperatures, while the deepest localization features were found at the highest available temperatures, overriding the influence of thermal activation and polarization fields.