The properties and deposition process of GaN films grown by reactive sputtering at low temperatures

Polycrystalline gallium nitride films, 100nmto1μm thick, were deposited under a range of conditions. Substrate electrode temperatures during sputtering were varied from room temperature to 450°C, the pressure from 0.15to6.0Pa, the nitrogen fraction of the deposition atmosphere from 10% to 100% and the target bias from −400to−1800V. The deposition rates as functions of these conditions are in the range 0.5–25nm∕min. The growth rate is considered to be controlled respectively by the thermally activated desorption from the substrate, changes in the mean free path and concentration of gas particles, differences between the sputter yields of Ga and GaN in Ar and N2, and changes in the ion current and sputter yields. The films are generally columnar, with the grain size increasing with film thickness. The most crystalline films were grown at mid range temperatures, low N2 concentrations, and low target biases, and the most disordered were grown at low pressures. The latter two cases suggest that decreasing the ...