Hysteretic Photochromic Switching (HPS) in Doubly Doped GaN(Mg):Eu-A Summary of Recent Results.

Paul Edwards,Jacob Leach,Michal Boćkowski,Menno Kappers,Katharina Lorenz,Katharina Lorenz,Katharina Lorenz,Kevin O’Donnell,Douglas Cameron,Akhilesh Singh,Akhilesh Singh,Mitsuo Yamaga

doi:10.3390/ma11101800

Abstract

Europium is the most-studied and least-well-understood rare earth ion (REI) dopant in GaN. While attempting to increase the efficiency of red GaN light-emitting diodes (LEDs) by implanting Eu+ into p-type GaN templates, the Strathclyde University group, in collaboration with IST Lisbon and Unipress Warsaw, discovered hysteretic photochromic switching (HPS) in the photoluminescence spectrum of doubly doped GaN(Mg):Eu. Our recent work, summarised in this contribution, has used time-, temperature- and light-induced changes in the Eu intra-4f shell emission spectrum to deduce the microscopic nature of the Mg-Eu defects that form in this material. As well as shedding light on the Mg acceptor in GaN, we propose a possible role for these emission centres in quantum information and computing.

Highlights

The doping of III-nitride semiconductors with rare earth ions, largely motivated by the promise of high-efficiency red GaN-based light-emitting diodes (LEDs), has a fairly recent history [1]
3.2, we describe of as-received GaN(Mg):Eu samples at room temperature, featuring mainly Eu0 luminescence, and Switching, revealed inSection the temperature dependence ofPhotochromic
A further clue regarding the nature of this distortion comes from the activation energy obtained from quantifying the light-induced switching of Eu0 to Eu1(Mg) at low T: this value (27.7 meV) is close to the barrier height predicted to exist between the two Mg acceptor states proposed by Lany and Zunger as the ‘curious case of the shallow MgGa deep state’ [4]

Summary

Introduction

The doping of III-nitride semiconductors with rare earth ions, largely motivated by the promise of high-efficiency red GaN-based LEDs, has a fairly recent history [1]. The p-type activation of GaN is well established, and underpins all commercial activities associated with the blue LED, the nature of the Mg acceptor remains controversial. First described in [2], we implanted Eu as a ‘spectator ion’ to probe the lattice location of Mg in GaN(Mg):Eu [3]. We observed photochromic switching between different configurations of an Eu-Mg defect. Linking the distinct Eu-Mg defect configurations with the shallow transient and deep ground states (STS and DGS) of the Mg acceptor, in the Lany–Zunger (L–Z) model [4], we determined an energy barrier of 27.7 meV for transitions between STS and DGS in agreement with theory.

Methods

Results

Discussion

Conclusion