Effect of Tensile Strain in GaN Layer on the Band Offsets and 2DEG Density in AlGaN/GaN Heterostructures

TL;DR

This study investigates how process-induced tensile strain in the GaN layer affects the band offsets and 2DEG density in AlGaN/GaN heterostructures, revealing strain's significant role in modulating polarization charge and electron density.

Contribution

It provides a detailed computational analysis showing strain can significantly enhance 2DEG density without altering band offsets in AlGaN/GaN heterostructures.

Findings

Strain does not significantly change band offsets.

Strain can increase 2DEG density by up to 25%.

Polarization charge modulation is key to density enhancement.

Abstract

We have addressed the existing ambiguity regarding the effect of process-induced strain in the underlying GaN layer on AlGaN/GaN heterostructure properties. The bandgaps and offsets for AlGaN on strained GaN are first computed using a cubic interpolation scheme within an empirical tight-binding framework. These are then used to calculate the polarization charge and two-dimensional electron gas density. Our bandstructure calculations show that it is not possible to induce any significant change in band offsets through strain in the GaN layer. The charge-density calculations indicate that such strain can, however, modulate the polarization charge and thereby enhance the 2DEG density at the AlGaN/GaN hetero-interface substantially, by as much as 25% for low Al mole fraction.