Cathodoluminescence studies of thermally oxidized cleaved surfaces of gallium selenide layered crystals

Abstract

Oxide layer formation on cleaved gallium monoselenide layer crystal surfaces during thermal oxidation in air have been studied by the cathodoluminescence (CL) method. GaSe surface heat treatment at temperatures up to 400 °C creates a significant decrease of CL intensity in the free exiton recombination band without any changes in the spectral structure. This is caused by an increase of the nonradiative surface recombination rate. During the thermal oxidation of GaSe cleaved surfaces at 400 °C < T < 600 °C the process of defect creation at the interface to the original structure takes place at first. The defect creation is accompanied by Ga2Se3 phase creation (at T > 450 °C). The main maximum of the CL band of this phase is at 1.45 eV. The β-Ga2O3 phase creation, which is identified according to its typical CL spectrum, takes place at T ≥ 600 °C. The CL intensity in this spectral part increases sharply and its maximum shifts from 3.10 to 3.45 eV with increasing oxidation time and temperature.