Optical investigation of electronic states of Mn4+ ions in p-type GaN

TL;DR

This study uses photoluminescence techniques to explore the electronic states of Mn4+ ions in p-type GaN, revealing intra-d-shell transitions and the Mn4+/3+ deep level, advancing understanding of Mn doping effects.

Contribution

It provides detailed spectroscopic characterization of Mn4+ electronic states and identifies the Mn4+/3+ deep level position in p-type GaN, which is novel for this material system.

Findings

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

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

Observation of intra-center excitation processes via PLE spectroscopy

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.