Luminescence distribution and hole transport in asymmetric InGaN multiple-quantum well light-emitting diodes

Asymmetric InGaN/GaN multiple-quantum well (MQW) light-emitting diodes were fabricated to expose the luminescence distribution and explore the hole transport. Under electrical injection, the sample with a wNQW active region in which the first QW nearest the p-side (QW1) is wider than the subsequent QWs shows a single long-wavelength light-emission peak arising from QW1. The inverse nWQW sample with a narrow QW1 shows one short-wavelength peak and one long-wavelength peak emitted separately from QW1 and the subsequent QWs. Increasing the barrier thickness between QW1 and the second QW (QWB1) in the nWQW structure, the long-wavelength peak is suppressed and the total light-emission intensity decreases. It was concluded that the nWQW and thin-QWB1 structure can improve the hole transport, and hence enhance the light-emission from the subsequent QWs and increase the internal quantum efficiency.