Optical and structural studies of homoepitaxially grown m-plane GaN

Abstract

Cathodoluminescence (CL) and transmission electron microscopy studies of homoepitaxially grown m-plane Mg-doped GaN layers are reported. Layers contain basal plane and prismatic stacking faults (SFs) with ∼106 cm−1 density. Broad emission peaks commonly ascribed to SFs were found to be insignificant in these samples. A set of quite strong, sharp lines were detected in the same spectral region of 3.36–3.42 eV. The observed peaks are tentatively explained as excitons bound to some impurity defects, which can also be related to SFs. Donor-acceptor pair (DAP) recombination involving Si or O and Mg was ruled out by fitting DAP energies and CL mapping.

Properties of the main Mg-related acceptors in GaN from optical and structural studies

“…The unusual situation that two different acceptor levels are created by one acceptor dopant in the case of Mg-doped GaN has prompted new structural investigations of GaN:Mg. 31,32 The observation that the second acceptor responsible for the ABE2 signature is only observed in highly doped GaN:Mg suggests the possibility of a correlation with structural defects, that have also been observed in the GaN:Mg samples studied here. 32 These structural defects appear only significantly for [Mg] > 10 18 cm…”

“…31,32 Some of these SF defects are very small in the c-plane samples (a couple of nm in size), and those could also be pyramid features, as reported for GaN:Mg grown on sapphire. 33 These defects are presumably induced during growth by the introduction of Mg atoms in the lattice.…”

Correlation between Si doping and stacking fault related luminescence in homoepitaxial m-plane GaN

“…On the other hand, SF-related lines have been detected in hetero-and homoepitaxially fabricated c-plane GaN doped with Mg. 11,12 However, no convincing cathodoluminescence (CL) lines related to the SF emissions have been found in most Mg-doped m-plane GaN, although electron microscopy analysis has confirmed a high density of both prismatic SFs (PSFs) and basal plane SFs (BSFs). 13 This points to a lack of clear understanding as to when and why SFs can be optically active in GaN. Since we have already reported results concerning luminescence of SFs in polar and non-polar homoepitaxial GaN doped by Mg, it is deemed natural to extend investigations to nonpolar homoepitaxial GaN layers with other types of dopants.…”

Luminescence of Acceptors in Mg-Doped GaN

“…Recent structural studies of c-plane and m-plane GaN:Mg layers grown by MOCVD on low defect bulk GaN substrates reveal a high density of nano-size basal plane stacking faults (BSFs) in such material, induced by the Mg-doping 5,6 . The interaction of the substitutional…”