THERMAL OXIDATION OF GaP AS A BASIS OF SELECTING THE CHEMICAL STIMULATING FUNCTIONS
Abstract
GaP, like other AIIIBV semiconductors (GaAs and InP), is a promising compound for the creation of photodiodes, photodetectors, and other microelectronics devices. The goal of this work is to reveal the peculiarities of thermal oxidation of GaP in comparison with GaAs and InP and to substantiate recommendations regarding the choice of chemical stimulators that intensify film formation processes and their modifying properties.
The thermal oxidation of GaP in oxygen proceeds at 650-750 °C (the duration of the process is 60 min.) and leads to the formation of nanosized films (no more than 100 nm). Thickness measurements are usually performed using the spectral ellipsometry method in the wavelength range of 350-550 nm. The measurements obtained by spectral ellipsometry can be confirmed by SEM. It was found that films predominantly consist of GaPO4 and Ga(PO3)3, above 725 °C, Ga2O3 was also identified (XRD and IRS methods).
According to the data from AFM and SEM, the surface of the films is heterogeneous, there are pores on it, the formation of which is associated with the evaporation of P2O5. The maximum pore depth reaches 80 nm (750 °C, 60 min), which practically coincides with the thickness of the oxide film according to the SE data (83 nm). The pore formation begins at 725 °C. Thus, the temperature of 750 °C is the upper limit of the range above which the thermal oxidation of GaP in oxygen is impractical due to the noticeable degradation of the films.
GaP differs from InP and GaAs by the formation of regular films of its oxide at higher temperatures (from 650 ° C), the absence of unoxidized substrate components (AES) and dielectric properties. Dielectric properties (specific resistance up to 1012 Ohm∙cm) of the films are due to the formation of gallium phosphates as a result of thermal oxidation of GaP. At the same time, a significant amount of Ga2O3 and In2O3 are contained in the films grown on the surfaces of GaAs and InP. The chemically stimulated thermal oxidation of GaP was proposed for the reduction of the temperature, increased growth rate, achievement of the required morphology of the surface, and wide variation of optical and electrophysical properties.
The use of a chemical stimulator will allow us: a) to increase the growth rate of the film with a simultaneous decrease in the operating parameters of the process (temperature, time) due to a change of the oxidation mechanism; b) control the morphology of the surface, composition, and properties (optical, electrophysical, etc.) of the formed films.
ACKNOWLEDGEMENTS
This work was financially supported by RFBR grant (projects Nos. 16-43-360595 р_а). The research results were obtained with equipment of Voronezh State University Centre for Collective Use of Scientific Equipment.
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