Excitons in the wurtzite AlGaN/GaN quantum-well heterostructures

TL;DR

This paper provides a theoretical analysis of exciton states and photoluminescence spectra in strained wurtzite AlGaN/GaN quantum wells, incorporating complex effects like deformation potential and spin-orbit interaction.

Contribution

It introduces a comprehensive theoretical model that accurately predicts exciton behavior and photoluminescence features in AlGaN/GaN quantum wells, aligning well with experimental data.

Findings

Red shift of photoluminescence peaks with increasing well width

Quantitative agreement with experimental photoluminescence data

Identification of exciton states active in optical absorption

Abstract

We have theoretically studied exciton states and photoluminescence spectra of strained wurtzite AlGaN/GaN quantum-well heterostructures. The electron and hole energy spectra are obtained by numerically solving the Schr\"odinger equation, both for a single-band Hamiltonian and for a non-symmetrical 6-band Hamiltonian. The deformation potential and spin-orbit interaction are taken into account. For increasing built-in field, generated by the piezoelectric polarization and by the spontaneous polarization, the energy of size quantization rises and the number of size quantized electron and hole levels in a quantum well decreases. The exciton energy spectrum is obtained using electron and hole wave functions and two-dimensional Coulomb wave functions as a basis. We have calculated the exciton oscillator strengths and identified the exciton states active in optical absorption. For different values of the Al content x, a quantitative interpretation, in a good agreement with experiment, is provided for (i) the red shift of the zero-phonon photoluminescence peaks for increasing the quantum-well width, (ii) the relative intensities of the zero-phonon and one-phonon photoluminescence peaks, found within the non-adiabatic approach, and (iii) the values of the photoluminescence decay time as a function of the quantum-well width.