Controlled growth of InGaN quantum dots on photoelectrochemically etched InGaN quantum dot templates

Abstract

Controlled growth of InGaN quantum dots (QDs) using photoelectrochemically (PEC) etched InGaN QD templates is demonstrated. The InGaN QDs are grown by a self-assembly (SA) method using metal-organic chemical vapor deposition on templates consisting of planar GaN and PEC etched InGaN QDs for comparison. The InGaN QD templates are formed using quantum-size-controlled PEC etching of planar InGaN layers on GaN, which produces controlled QD radiuses with a statistical mean (μ) of 17.3 nm and standard deviation (σ) of 6.2 nm, and densities of 1.2 × 1010 cm−2. The PEC etched QDs are capped with an AlGaN interlayer and GaN barrier layer to recover a planar surface morphology for subsequent SA growth of QDs. The PEC QD templates behave as seeds via localize strain near the PEC QDs which provide improved control of the SA QD growth. The SA grown QDs on PEC QD templates are smaller and have controlled radiuses with μ = 21.7 nm and σ = 11.7 nm compared to the SA QDs on planar GaN templates with radiuses of μ = 37.8 nm and σ = 17.8 nm. Additionally, the dot densities of the SA QDs on PEC QD templates are ~3 times higher and more closely match the underlying densities of the template (8.1 × 109 cm−2). Multiple quantum dots (MQDs) are also grown on both templates that consist of 4 periods of SA QDs and AlGaN/GaN interlayer/barrier layers. The MQDs grown on PEC QD templates better retain their planarized smooth surfaces after barrier layer growth, and exhibit ~3 times stronger PL intensity at room temperature compared to MQDs grown on planar GaN.