On the internal quantum efficiency for InGaN/GaN light-emitting diodes grown on insulating substrates

The internal quantum efficiency (IQE) for InGaN/GaN lightemitting diodes (LEDs) grown on [0001] sapphire substrates is strongly affected by various factors including polarization effect in the InGaN/GaN multiple quantum wells (MQWs), insufficient electron and hole injections, low p-type GaN doping efficiency, carrier loss due to the Auger recombination, and current crowding effect especially for the hole current in the p-GaN region. In this work, the remedies taken by the scientific community to enhance the IQE are reviewed, compared and summarized. Meanwhile, this review also discusses alternative ways including polarization self-screening effect, polarization cooling, hole accelerator, and hole modulator. The structural solutions we propose in this work can better improve the device performance without increasing the processing difficulty significantly, and their effectiveness in improving the IQE is further supported by the numerical and experimental studies. For example, on the contrary to common belief, the polarizations in the [0001] oriented InGaN/GaN LEDs can be advantageously used to improve the device performance based on our designs. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim