Anisotropic structural and optical properties of a-plane (11-20) AlInN nearly-lattice-matched to GaN

TL;DR

This study demonstrates the epitaxial growth and characterization of nearly-lattice-matched a-plane AlInN layers on GaN, revealing anisotropic optical properties and strain effects relevant for optoelectronic applications.

Contribution

It presents a method to grow nearly-lattice-matched a-plane AlInN on GaN and analyzes its anisotropic structural and optical properties, including strain and bandgap differences.

Findings

Achieved nearly-lattice-matched AlInN at 760°C with x=0.19

Identified a 140 meV bandgap difference between polarization directions

Observed a room-temperature PL peak at 3.38 eV with strong polarization

Abstract

We report epitaxial growth of a-plane (11-20) AlInN layers nearly-lattice-matched to GaN. Unlike for c-plane oriented epilayers, a-plane Al_{1-x}In_{x}N cannot be simultaneously lattice-matched to GaN in both in-plane directions. We study the influence of temperature on indium incorporation and obtain nearly-lattice-matched Al_{0.81}In_{0.19}N at a growth temperature of 760^{o}C. We outline a procedure to check in-plane lattice mismatch using high resolution x-ray diffraction, and evaluate the strain and critical thickness. Polarization-resolved optical transmission measurements of the Al_{0.81}In_{0.19}N epilayer reveal a difference in bandgap of ~140 meV between (electric field) E_parallel_c [0001]-axis and E_perpendicular_c conditions with room-temperature photoluminescence peaked at 3.38 eV strongly polarized with E_parallel_c, in good agreement with strain-dependent band-structure calculations.