Performance Enhancement of InGaN/GaN MQWs with n-AlGaN Interlayer Grown on Nano-Patterned Sapphire Substrate

The lateral light emitting diodes (LEDs) fabricated on insulated sapphire substrate usually suffer current crowding effect, which would lead to a serious degeneration of luminescence properties and reliability issues. To relieve the current crowding effect and improve the device performance, n-AlGaN interlayers with gradual changing Al fractions were introduced into the n-GaN layer of the green LEDs. The gradually decreased Al composition in the introduced n-AlGaN interlayer resulted in a barrier in the conduction band, which could promote a more uniform distribution of electrons along the horizontal direction and then reduce the current crowding effect. In addition, the AlGaN/GaN heterojunction produced large amounts of two-dimensional electron gas at the interface, which could balance the electron distribution at the AlGaN/GaN interface and reduce the current crowding effect as well. The introduced current spreading process improved the luminescence intensity of LED. Ultimately, electroluminescence spectra were measured and confirmed the improved luminescence intensity via gradually decreased Al composition in the introduced n-AlGaN interlayer.