The Roles of Structural Imperfections in InGaN-Based Blue Light-Emitting Diodes and Laser Diodes

TLDR

InGaN active layers enable high‑efficiency LEDs across the visible spectrum, replacing GaN to produce amber, green, blue, and ultraviolet light. Localized energy states from indium composition fluctuations in InGaN, together with lateral GaN overgrowth on sapphire that reduces threading dislocations, underpin the devices’ high efficiency. Blue and green InGaN quantum‑well LEDs achieve 5 and 30 lm W⁻¹ despite threading dislocation densities of 10⁸–10¹² cm⁻², while InGaN multi‑quantum‑well laser diodes on GaN above SiO₂ masks exceed 10 000 h lifetime but exhibit higher threshold currents with increased dislocations.

Abstract

REVIEW High-efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layer. The localized energy states caused by In composition fluctuation in the InGaN active layer are related to the high efficiency of the InGaN-based emitting devices. The blue and green InGaN quantum-well structure light-emitting diodes with luminous efficiencies of 5 and 30 lumens per watt, respectively, can be made despite the large number of threading dislocations (1 × 10 8 to 1 × 10 12 cm −2 ). Epitaxially laterally overgrown GaN on sapphire reduces the number of threading dislocations originating from the interface of the GaN epilayer with the sapphire substrate. InGaN multi-quantum-well structure laser diodes formed on the GaN layer above the SiO 2 mask area can have a lifetime of more than 10,000 hours. Dislocations increase the threshold current density of the laser diodes.