High-reflectance III-nitride distributed Bragg reflectors grown on Si substrates

TL;DR

This paper reports the successful growth of high-reflectance III-nitride distributed Bragg reflectors directly on silicon substrates, achieving record reflectance and enabling advanced optoelectronic devices on silicon.

Contribution

It presents the first high-reflectance III-nitride DBR grown directly on Si substrates, surpassing theoretical reflectance and addressing strain issues for device integration.

Findings

Peak reflectance of 96.8% on Si substrate

Exceeds theoretical reflectance of 96.1%

Crack-free growth of 500 nm GaN on DBR

Abstract

Distributed Bragg reflectors (DBRs) composed of an AlN/AlGaN superlattice were grown of Si (111) substrates. The first high-reflectance III-nitride DBR on Si was achieved by growing the DBR directly on the Si substrate to enhance the overall reflectance due to the high index of refraction contrast at the Si/AlN interface. For a 9x DBR, the measured peak reflectance of 96.8% actually exceeded the theoretical value of 96.1%. The AlN/AlGaN superlattice served the added purpose of compensating the large tensile strain developed during the growth of a crack-free 500 nm GaN / 7x DBR / Si structure. This achievement opens the possibility to manufacture high-quality III-nitride optoelectronic devices without optical absorption in the opaque Si substrate.