Shifting donor-acceptor photoluminescence in N-doped ZnO

TL;DR

This study investigates how different epitaxial growth methods affect the photoluminescence properties of nitrogen-doped ZnO films, revealing inhomogeneity effects and acceptor activation energy independent of nitrogen concentration.

Contribution

It demonstrates the impact of growth technique on impurity distribution in N-doped ZnO and evaluates the acceptor activation energy.

Findings

Inhomogeneity in impurity distribution varies with growth method.

Better electrical properties correlate with smaller inhomogeneity.

Acceptors have an activation energy of approximately 170 meV, unaffected by nitrogen levels.

Abstract

We have grown nitrogen-doped ZnO films grown by two kinds of epitaxial methods on lattice-matched ScAlMgO$_4$ substrates. We measured the photoluminescence (PL) of the two kinds of ZnO:N layers in the donor-acceptor-pair transition region. The analysis of excitation-intensity dependence of the PL peak shift with a fluctuation model has proven that our observed growth-technique dependence was explained in terms of the inhomogeneity of charged impurity distribution. It was found that the inhomogeneity in the sample prepared with the process showing better electrical property was significantly smaller in spite of the similar nitrogen concentration. The activation energy of acceptor has been evaluated to be $\approx 170$ meV, which is independent of the nitrogen concentration.