Piezoelectric field in InGaN-based quantum wells grown on c-plane sapphire substrates measured by electroreflectance spectroscopy: from near-ultraviolet to green spectra.

The internal electric field caused by the strain-induced piezoelectric polarization in InGaN-based single- or multiple-quantum-well light-emitting diodes (LEDs) is measured by using electroreflectance spectroscopy. The piezoelectric fields (F_PZ’s) in InGaN LEDs from near-ultraviolet to green spectra (In-compositions of ∼3% to ∼30%) are measured to understand the effect of In-composition on F_PZ. A second-order polynomial as a function of In-composition is proposed from these F_PZ values as a guideline for future research. The experimental trend has a good agreement with the theoretical prediction for low (<15%) In-compositions. However, the trend diverges from the theoretical prediction at high In-compositions due to defect incorporation into the lattice. The observed effects of epitaxial structures and point defects on F_PZ are systematically explained. [ABSTRACT FROM AUTHOR]