On the integrated p-type region free of electron blocking layer for AlGaN-based deep-ultraviolet light emitting diodes

Abstract

AlGaN-based deep-ultraviolet light emitting diodes (DUV-LEDs) with thin p-GaN capping layer have been one of the most promising configurations, thanks to their excellent light extraction potential, which are, however, generally accompanied by insufficient hole supply. In this work, multi-graded p-AlGaN layers are adopted as an integrated p-type region, in which the electron blocking layer (EBL) is taken off to promote the carrier transport. The experimental results show that both the operation voltage and light output power of the DUV-LEDs are improved compared to the traditional ones, leading to a remarkable increase (by 114%) in their wall-plug efficiency. Further analysis confirms that the integrated p-type region serving as the hole supply layer helps holes to avoid the barrier between the p-GaN and integrated p-type region during their transport, and the absence of the EBL further eliminates part of the obstacles for hole drifting, giving rise to an enhanced hole concentration in quantum wells. Meanwhile, thanks to the modulation of the negative polarization induced bulk charges for conduction band, which is introduced within the integrated p-type region, the electron leakage is effectively suppressed even without the EBL, thus improving the device performance dramatically.