Comparison of high quality GaN‐based light‐emitting diodes grown on alumina‐rich spinel and sapphire substrates

Abstract

High quality GaN-based light-emitting diodes (LEDs) can be achieved on alumina-rich spinel (MgAl 6 O 10 ), a new substrate material with better thermal and lattice match to GaN than sapphire. As alumina-rich spinel is chemically very close to sapphire (Al 2 O 3 ), the GaN metal-organic chemical vapour deposition (MOCVD) conditions developed for c-plane sapphire have been successfully replicated on it. In this article, we report on the electroluminescence (EL) properties of GaN-based LEDs grown by MOCVD simultaneously on Al 2 O 3 -(0001) and MgAl 6 O 10 -(111). Both devices exhibit a linear increase of the light output power versus current density, with a higher EL-intensity and a narrower EL-linewidth for the LEDs grown on alumina-rich spinel. However, due to the lower thermal conductivity of spinel, these LEDs start suffering from device heating at lower current densities than on sapphire. Irreversible damage occurs for DC current densities of ∼ 0.9 kA/cm² and at an estimated junction temperature of ∼ 325 °C.

Structure, thermal expansion and optical property of alumina-rich spinel substrate

“…In addition, the growth temperature of the 1:3 spinel is lower about 100-200 • C than that of MgAl 2 O 4 , which is in favor of crystal growth. Tinjod et al [11] reported that the GaN-based LEDs grown by MOCVD on 1:3 spinel-(1 1 1) exhibit a higher EL-intensity and a narrower EL-linewidth than those grown on Al 2 O 3 . 1:3 spinel is a promising substrate material for GaN epitaxial growth.…”