Journal of Physical Studies 1(1), 101–105 (1996) DOI: https://doi.org/10.30970/jps.01.101 FORMATION OF THE OXIDE LAYER BY THE THERMAL OXIDATION OF CLEVAGE SURFACE IN THE GALLIUM SELENIDE LAYERED CRYSTAL

V. Savchyn, J. Stakhira
Ivan Franko Lviv State University, Chair of Semiconductor Physics
50 Drahomanov Str., Lviv UA-290005, Ukraine

Processes of the oxide layer formation on the clevage surface of gallium monoselenide layer crystal at the thermal oxidation in the air have been studied by the cathodoluminescence (CL) method. Heat treatment of the GaSe surface at the temperature up to $400^\circ$C leads to a significant decrease in the CL intensity in the free exiton recombination band without any changes in the spectrum structure. This is caused by unemissive surface recombination rate increasing due to the arising of the GaSe surface absorption activity at the temperature increase.

In the process of thermal oxidation of the GaSe cleavage surface on the interface at $400450^\circ$C). The base maximum of this phase CL band is at 1.45 eV. The $β$-Ga$_2$O$_3$ phase creation is carried out at $T\geq 600^\circ$C. The CL intensity in the spectrum part increases sharply and its maximum shifts from 3.10 to 3.45 eV with the increasing oxidation temperature and time. At $T>700^\circ$C the $Ga Se$ surface is almost fully oxidized with $β$-Ga$_2$O$_3$ and SeO$_2$ creation, the latter evaporating from the surface.

The information about the distribution of structural fragments in the described TO layer responsible for certain bands in the CL spectra was obtained by changing electron depth penetration (at varying electron energy). So at $700^\circ$C oxidation temperature during 0.25 hour the interface of TO-GaSe is formed at the depth of nearly $400-500$ nm from the surface and is localized in the $100-150$ nm thick layer. Its structure and phase composition smoothly change with depth.

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