High quality AlN film assisted by graphene/sputtered AlN buffer layer for deep-ultraviolet-LED

Abstract

The advantages of van der Waals epitaxial nitrides have become a research hot topic. It is worth noting that graphene plays an important role in the research of epitaxial AlN epitaxial layer. In this work, we demonstrate a method to obtain high-quality and low-dislocation AlN epitaxial layer by combining graphene and sputtered AlN as the nucleation layer on the C-sapphire substrate via metal organic chemical vapor deposition, and successfully fabricated a 277 nm AlGaN-based deep ultraviolet light emitting diode (DUV-LED) based on the obtained AlN epitaxial layer. The presence of graphene promotes the stress release of AlN. Compared with the AlN epitaxial layer directly grown on graphene/sapphire substrate, the exist of sputtered AlN/graphene nucleation layer facilitates most of the threading dislocations in AlN can annihilate each other in the range of about 100 nm. Thus, as grown AlN epitaxial layer shows the decreasing of the screw dislocation from 2.31 × 109 to 2.08 × 108 cm−2 significantly. We manufacture an DUV-LED with 277 nm emission wavelength by using high-quality AlN films, which shows that magnitude of the leakage current is only on the order of nanoamperes and the forward turn on voltage is 3.5 V at room temperature. This study provides a meaningful strategy to achieve high-quality AlN film and high-performance DUV-LED.