Temperature dependence of the piezoelectric field in GaInN/GaN quantum wells and its impact on the device performance

Temperature-dependent piezoelectric-field characteristics of GaInN/GaN blue quantum wells are experimentally investigated between 100 and 300 K. The results show that the magnitude of the piezoelectric field increases with decreasing temperature with a slope of 1.08 kV cm−1 K−1 due to the increase in a mismatch between thermal expansion coefficients. To understand the impact of temperature-dependent piezoelectric field on the device performance, the external quantum efficiencies (EQEs) of a blue light-emitting diode are measured in the same temperature range. More severe EQE droops are observed at lower temperatures, which can be attributed to the increase in carrier overflow/spill-over to the p-clad layer enhanced by the stronger piezoelectric fields. The larger blueshifts in mean photon energy are simultaneously observed at lower temperatures, which also confirms the stronger piezoelectric fields at lower temperatures.