BInGaN alloys nearly lattice-matched to GaN for high-power high-efficiency visible LEDs

TL;DR

This study uses computational methods to explore BInGaN alloys, which are nearly lattice-matched to GaN, aiming to enable high-power, efficient visible LEDs with thicker active layers by reducing lattice mismatch.

Contribution

The paper provides a predictive analysis of BInGaN alloys, demonstrating their potential for lattice matching and tunable electronic properties suitable for high-power LEDs.

Findings

BInGaN alloys with B:In ratio of 2:3 are nearly lattice matched to GaN.

Solubility of boron is higher in InGaN than in GaN.

Adjustable band gaps from 1.75 to 3.39 eV cover the visible spectrum.

Abstract

InGaN-based visible LEDs find commercial applications for solid-state lighting and displays, but lattice mismatch limits the thickness of InGaN quantum wells that can be grown on GaN with high crystalline quality. Since narrower wells operate at a higher carrier density for a given current density, they increase the fraction of carriers lost to Auger recombination and lower the efficiency. The incorporation of boron, a smaller group-III element, into InGaN alloys is a promising method to eliminate the lattice mismatch and realize high-power, high-efficiency visible LEDs with thick active regions. In this work we apply predictive calculations based on hybrid density functional theory to investigate the thermodynamic, structural, and electronic properties of BInGaN alloys. Our results show that BInGaN alloys with a B:In ratio of 2:3 are better lattice matched to GaN compared to InGaN and, for indium fractions less than 0.2, nearly lattice matched. Deviations from Vegard's law appear as bowing of the in-plane lattice constant with respect to composition. Our thermodynamics calculations demonstrate that the solubility of boron is higher in InGaN than in pure GaN. Varying the Ga mole fraction while keeping the B:In ratio constant enables the adjustment of the (direct) gap in the 1.75-3.39 eV range, which covers the entire visible spectrum. Holes are strongly localized in non-bonded N 2p states caused by local bond planarization near boron atoms. Our results indicate that BInGaN alloys are promising for fabricating nitride heterostructures with thick active regions for high-power, high-efficiency LEDs.