Is It Possible to Make Thin p-GaN Layer for AlGaN-Based Deep Ultraviolet Micro Light Emitting Diodes?

Abstract

In this work, AlGaN-based deep ultraviolet micro-light-emitting diode (DUV <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED) with a thin p-GaN layer is proposed to improve the electrical and optical performances. The experimental and calculated results prove that, besides the significantly enhanced light extraction efficiency (LEE) caused by the reduced absorption for DUV light, the thin p-GaN layer design can also slightly suppress the current spreading effect for the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED, which will keep the holes away from the defected region of mesa sidewalls. Then, the surface nonradiative recombination at the mesa edge can be mildly suppressed and thus the hole injection is also enhanced though not remarkably, which favors the radiative recombination in active region. As a result, the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED with thin p-GaN layer has the enhanced external quantum efficiency (EQE) and the improved optical power when compared to the DUV <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> LED with thick p-GaN layer. The on/off current ratio is increased to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{7}}$ </tex-math></inline-formula> from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{6}}$ </tex-math></inline-formula> , which infers that defect-caused leakage current is reduced on the mesa sidewalls.