The role of hydrostatic stress in determining the bandgap of InN epilayers

TL;DR

This study investigates how hydrostatic stress in InN epilayers influences their optical properties, revealing that internal stress causes bandgap shifts which could explain variability in reported values.

Contribution

It establishes a direct correlation between hydrostatic stress and optical bandgap shifts in InN epilayers grown under different conditions.

Findings

Hydrostatic stress causes a measurable shift in the band edge.

Internal stress correlates with changes in photoluminescence emission.

Variations in InN bandgap in literature may be due to internal stress effects.

Abstract

We establish a correlation between the internal stress in InN epilayers and their optical properties such as the measured absorption band edge and photoluminescence emission wavelength. By a careful evaluation of the lattice constants of InN epilayers grown on c-plane sapphire substrates under various conditions by metalorganic vapor phase epitaxy we find that the films are under primarily hydrostatic stress. This results in a shift in the band edge to higher energy. The effect is significant, and may be responsible for some of the variations in InN bandgap reported in the literature.