Universal behavior of photoluminescence in GaN-based quantum wells under hydrostatic pressure governed by built-in electric field

摘要

Correlation between the photoluminescence (PL) energy at ambient pressure and the pressure coefficient of photoluminescence is studied in quantum wells (QWs) based on nitride alloys, such as InGaN/GaN, GaN/AlGaN, and GaN/InAlN, grown along the polar direction [0001] of the wurtzite structure. Analyzing previously published and new experimental data, we have found that for InGaN/GaN QWs independent of In content (in the range between 6% and 25%) and also QW number and QW width, a linear relationship between these two parameters occurs. The presented experimental results are in agreement with numerical calculations carried out in the framework of the k⃗∙p⃗ method with excitonic effects, provided that nonlinear piezoelectricity and nonlinear elasticity are taken into account. The performed analytical analysis indicates that the slope of the linear relationship between the pressure coefficient of photoluminescence and the photoluminescence energy at ambient pressure is determined by the logarithmic derivative of the built-in electric field with respect to pressure. Then, we show that the pressure coefficient of photoluminescence depends linearly on the photoluminescence energy at ambient pressure also in GaN/AlGaN and GaN/InAlN QWs. In GaN/AlGaN QWs, the slope of this dependence slightly decreases with Al content in the barriers. For GaN/InAlN QWs, we predict an unusual dependence of this slope on In content, which is associated with the vanishing built-in electric field in structures with 30% of In. For all studied nitride systems, a reasonable agreement between the experimental and theoretical results is achieved when the effects of nonlinear piezoelectricity and nonlinear elasticity are taken into account.