Luminescence energy and carrier lifetime in InGaN/GaN quantum wells as a function of applied biaxial strain

Continuous-wave and time-resolved photoluminescence of InGaN quantum wells are measured as a function of applied biaxial strain, which provides a unique means of altering the built-in polarization field in these structures. The direction and magnitude of the shift of the luminescence-peak energy are quantitatively analyzed within an analytical carrier separation model. It is found that the presently used piezoelectric coefficients of InGaN are not entirely consistent with our experimental results. Instead, consistent interpretation of our data requires the $e_{13}$ and $e_{33}$ piezoelectric coefficients of InN to be ∼15% larger than the commonly accepted values. Our analysis allows the assignment of an effective carrier-separation parameter to each investigated quantum-well sample, which quantifies the shift of the luminescence peak energy with the change in the polarization field. The effective carrier separation is found to be zero for narrow quantum wells (<1.5 nm) and asymptotically approaches the full quantum well width for increasing well width. However, heavy doping or increased indium content are found to reduce the effective carrier separation, which is ascribed to screening of the polarization field or localization effects, respectively. A reduction of the carrier lifetime with the application of strain supports the carrier separation model and allows the derivation of a quantity related to the change of the wave function shape with the polarization field.