Effect of giant electric fields on the optical properties of GaN quantum wells

Abstract

Spontaneous and piezoelectric fields are known to be the key to understanding the optical properties of nitride heterostructures. This effect modifies the electronic states in the quantum well (QW) and the emission energy in the photoluminescence (PL) spectrum. These fields induce a reduction in the oscillator strength of the transition energy between the confined electron and hole states in GaN/Al$_{x}$Ga$_{1 - x}$N QWs, and dramatically increase the carrier lifetime as the QW thickness increases. In this work, we solve analytically the Schrödinger equation for moderate electric fields when the electron-hole transition energy in the QW is larger than the energy gap of the GaN. Furthermore, the large redshifts of the PL energy position and the spatial separation of the electrons and holes several greater times than the Bohr radius caused by the strong piezoelectric fields are explained using a triangular potential, instead of a square one, in the Schrödinger equation. The transition energy calculations between the electron-hole pair as a function of the well width with the electric field as a fitting parameter are in agreement with the measured photoluminescence energy peaks.