Hydride Vapor Phase Epitaxy of GaN on Silicon Covered by Nanostructures

TL;DR

This study demonstrates a two-step hydride vapor phase epitaxy process for growing GaN on silicon substrates covered with nanostructures, revealing insights into defect formation and growth modes influenced by the template structure.

Contribution

It introduces a novel two-step HVPE process on nanostructured templates, showing how growth conditions affect defect dynamics and epitaxial quality.

Findings

Stacking faults form during low-temperature HVPE and disappear at high temperature.

Luminescence features provide insights into the growth process.

Growth mode depends on the specific AlN/GaN template structure.

Abstract

Several ten $\mu$m GaN have been deposited on a silicon substrate using a two-step hydride vapor phase epitaxy (HVPE) process. The substrates have been covered by AlN layers and GaN nanostructures grown by plasma-assisted molecular-beam epitaxy. During the first low-temperature (low-T) HVPE step, stacking faults (SF) form, which show distinct luminescence lines and stripe-like features in cathodoluminescence images of the cross-section of the layers. These cathodoluminescence features allow for an insight into the growth process. During a second high-temperature (high-T) step, the SFs disappear, and the luminescence of this part of the GaN layer is dominated by the donor-bound exciton. For templates consisting of both a thin AlN buffer and GaN nanostructures, a silicon incorporation into the GaN grown by HVPE is not observed. Moreover, the growth mode of the (high-T) HVPE step depends on the specific structure of the AlN/GaN template, where in a first case, the epitaxy is dominated by the formation of slowly growing facets, while in a second case, the epitaxy proceeds directly along the c-axis.