Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors

Abstract

We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli's exclusion's principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction ⌶ 0 = 3.4Ϯ 0.2 meV. This value dictates the splitting between the ground-state line I 1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, −0.4Ϯ 0.1 and 0.2Ϯ 0.1 meV. In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.

Optical signature of Mg-doped GaN: Transfer processes

“…In recent years the development of solid state light emitters for the blue to ultraviolet (UV) spectral range has caught rising interest which naturally results in the task of bipolar doping of intermediate and wide bandgap materials like CdS, [1][2][3] ZnSe, 4 ZnO 5-7 and GaN. 1,8 Up to date only GaN and its ternary systems InGaN and AlGaN have matured towards technologically relevant applications as e.g.…”

“…1,8 Up to date only GaN and its ternary systems InGaN and AlGaN have matured towards technologically relevant applications as e.g. blue and near UV light-emitting diodes 9,10 and blue laser diodes as originally invented by Nakamura et al 11,12 While sufficient n-type conduction for light emitting devices was achieved in the early years of GaN growth, p-type doping with resulting predominant p-type conduction was an outstandingly challenging task until the breakthrough of Amano et al, 8 and Akasaki et al 13 The first p-conducting GaN samples where doped with Mg and subsequently activated by low energy electron beam irradiation (LEEBI) in order to remove the acceptor passivating hydrogen which originates from the metal organic chemical vapor deposition (MOCVD) growth procedure.…”

“…2,3,21 Studying the luminescence traces of Mg doped GaN with different compensation, doping and strain levels 22,23 has been proven as an effective tool for improving the growth procedures themselves but has also raised general questions concerning the twofold occurrence and stability 24 of acceptors in such wide bandgap materials. Rising interest in this dual nature of acceptors in GaN has just recently been triggered by publications of Monemar et al 25 and Lany et al 26 which led to novel insight concerning the general topic of acceptor doping in wide bandgap materials as also discussed by Gil et al 1 for the case of CdS and GaN. Two Mg related acceptors were observed by photoluminescence (PL) spectroscopy 25 and assigned to one regular substitutional acceptor and one, under UV laser illumination unstable, Mg acceptor complex.…”

Modeling of the Interminiband Absorption Coefficient in InGaN Quantum Dot Superlattices

“…In MQDs' structure in which each nanostructure can be assumed as a single QD (the absence of wavefunction overlap among those of different QDs), the main absorption coefficient component is related to QDs' bound excitons [35,43,47,[49][50][51][52]. Instead, in this paper, our investigation is focused on absorption coefficient components derived by thesuperlattice nature of high density QD heterostructures.…”

Photoluminescence of Mg-doped m -plane GaN grown by MOCVD on bulk GaN substrates

“…The doublet line ABE1 is due to Mg contamination in the growth system. It was recently demonstrated that acceptor BEs (ABEs) in wurtzite wide bandgap semiconductors are expected to exhibit several radiative states 7 . Fig.…”