Effect of different buffer layers on the quality of InGaN layers grown on Si

TL;DR

This study investigates how different buffer layers affect the structural, optical, and electrical properties of InGaN layers grown on silicon, demonstrating improved quality with AlN buffers and potential for simplified solar cell fabrication.

Contribution

It introduces the use of radical-beam irradiation for high-quality InGaN growth on Si and identifies optimal buffer layers for device performance.

Findings

AlN buffer layer improves InGaN quality

Radical-beam irradiation eliminates droplets

Enables fabrication of simplified InGaN/Si solar cells

Abstract

This work studies the effect of four different types of buffer layers on the structural and optical properties of InGaN layers grown on Si(111) substrates and their correlation with electrical characteristics. The vertical electrical conduction of n-InGaN/buffer-layer/p-Si heterostructures, with In composition near 46%, which theoretically produces an alignment of the bands, is analyzed. Droplet elimination by radical-beam irradiation was successfully applied to grow high quality InGaN films on Si substrates for the first time. Among several buffer choices, an AlN buffer layer with a thickness above 24 nm improves the structural and optical quality of the InGaN epilayer while keeping a top to bottom ohmic behavior. These results will allow fabricating double-junction InGaN/Si solar cells without the need of tunnel junctions between the two sub-cells, therefore simplifying the device design.