UVC LEDs on Bulk AlN Substrates Using Silicon Nanomembranes for Efficient Hole Injection

TL;DR

This paper demonstrates a UVC LED emitting at 237 nm with high power and efficiency, achieved through high-quality AlN substrates and p-type silicon nanomembrane contacts, enabling improved hole injection and device performance.

Contribution

It introduces the use of p-Si nanomembranes for hole injection in UVC LEDs on bulk AlN substrates, enabling shorter wavelength emission with high power and efficiency.

Findings

Record 265 μW light output at 237 nm

No efficiency droop up to 245 A/cm²

Dominant emission at 237 nm with minimal parasitic emissions

Abstract

As UV LEDs are explored at shorter wavelengths (< 280 nm) into the UVC spectral range, the crystalline quality of epitaxial AlGaN films with high Al compositions and inefficient hole injection from p-type AlGaN severely limit the LED performance and development. In this work, we report on 237 nm light emission with a record light output power of 265 uW from AlN/Al0.72Ga028N multiple quantum well UVC LEDs using bulk AlN substrates and p-type silicon nanomembrane contact layers for significantly improved AlGaN film quality and hole injection, respectively. No intensity degradation or efficiency droop was observed up to a current density of 245 A/cm2, which is attributed to the low dislocation density within AlGaN films, the large concentration of holes from p-Si, and efficient hole-transport to the active region. Additionally, the emission peak at 237 nm is dominant across the electroluminescence spectrum with no significant parasitic emissions observed. This study demonstrates the feasibility of using p-Si as a hole injector for UVC LEDs, which can be extended to even shorter wavelengths where hole injection from chemically doped AlGaN layers is not feasible.