Optical characterization studies of grown-in defects in ZnO epilayers grown by molecular beam epitaxy

Abstract

Defect formation in ZnO epilayers grown by molecular beam epitaxy (MBE) is studied by employing optical characterization techniques such as photoluminescence (PL) and optically detected magnetic resonance (ODMR). Excess of oxygen during the growth was found to cause an appearance of the PL peak at around 3.338 eV, which indicates that the corresponding defects are predominantly formed in O-rich ZnO. On the other hand, non-stoichiometry during the growth was singled out as the main factor facilitating formation of defects involved in the yellow PL emission band peaking at around 2.17 eV. Several magnetic-resonance active defects are revealed via monitoring this emission and their magnetic-resonance signatures are obtained.