Electronic states of Mn4+ ions in p-type GaN

TL;DR

This study investigates the electronic states of Mn4+ ions in p-type GaN using photoluminescence techniques, revealing intra d-shell transitions, charge-transfer processes, and the Mn4+/3+ deep level position, advancing understanding of Mn doping in GaN.

Contribution

The paper provides detailed spectroscopic analysis of Mn4+ states in p-GaN, identifying intra-shell transitions and the Mn4+/3+ deep level, which was not previously characterized in this context.

Findings

Sharp PL lines at 1.0 eV attributed to Mn4+ intra d-shell transition.

Identification of Mn4+/3+ deep level at 1.11 eV above valence band.

Observation of intra-center excitation processes via specific Mn4+ excited states.

Abstract

The electronic states of manganese in p-type GaN are investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. A series of sharp PL lines at 1.0 eV is observed in codoped GaN and attributed to the intra d-shell transition 4T2(F)-4T1(F) of Mn4+ ions. PLE spectrum of the Mn4+ [4T2(F)-4T1(F)] luminescence reveals intra-center excitation processes via the excited states of Mn4+ ions. PLE peaks observed at 1.79 and 2.33 eV are attributed to the intra d-shell 4T1(P)-4T1(F) and 4A2(F)-4T1(F) transitions of Mn4+, respectively. In addition to the intra-shell excitation processes, a broad PLE band involving charge-transfer transition of the Mn4+/3+ deep level is observed, which is well described by the Lucovsky model. As determined from the onset of this PLE band, the position of the Mn4+/3+ deep level is 1.11 eV above the valence band maximum, which is consistent with prior theory using ab initio calculations. Our work indicates 4+ is the predominant oxidation state of Mn ions in p-type GaN:Mn when the Fermi energy is lower than 1.11 eV above the valence band maximum.