Defects in AlN: High-frequency EPR and ENDOR studies

Abstract

Compensation by deep-level defects and self-compensation of shallow donors in AlN are discussed in the light of results of a high-frequency pulse electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) study. It was suggested on the basis of the large mostly isotropic hyperfine interaction with A(27Al)=406 MHz that one of the deep-level defect is isolated interstitial Al2+ atom. Two types of effective-mass-like shallow donors with a delocalised wave function were shown to exist in unintentionally doped AlN. The experiments demonstrate how the transformation from a shallow donor to a deep (DX) centre takes place and how the deep DX centre can be reconverted into a shallow donor forming a spin triplet and singlet states with an exchange interaction of about 24 cm-1 and with a lowest triplet state. © 2009 Elsevier B.V. All rights reserved