Optical Properties of Sputter-Deposited Tungsten-Doped Gallium Oxide Thin Films

Gallium oxide (Ga$_{2}$O$_{3})$ finds attractive applications in luminescent phosphors, high temperature sensors, antireflection coatings, and solar cells. With a band gap of $\sim$5 eV, Ga$_{2}$O$_{3}$ has been recognized as a deep ultraviolet transparent conducting oxide, which makes the material a potential candidate for transparent electrode applications in UV optoelectronics. In this work, effect of tungsten (W) doping on the structure and optical properties of Ga$_{2}$O$_{3}$ has been investigated. W-metal doped $\beta $-Ga$_{2}$O$_{3}$ films grown by sputter deposition by varying the sputtering power from 50-100 W to vary tungsten concentration in the films. The samples were deposited on to Si(100) and quartz substrates by keeping the growth temperature constant at 500 $^{\circ}$C. It is seen that increasing W concentration alters the electronic structure of Ga$_{2}$O$_{3}$ while the crystal structure of $\beta $-Ga$_{2}$O$_{3}$ phase is retained. Spectrophotometry analysis indicates that the W-doped Ga$_{2}$O$_{3}$ films are highly transparent. The fundamental absorption edge shifts associated with a decrease in band gap energy. The results will be presented and discussed.