Bandgap tuning and spectroscopy analysis of In_xGa_(1−x)N thin films grown by RF sputtering method

In this study, we present a simple and novel method for optical bandgap tuning of indium gallium nitride (InGaN) thin films by controlling the growth conditions in magnetron RF sputtering. Thin films with different indium (In) atomic compositions, x = 0.02 to 0.57 are deposited on high temperature aluminosilicate glass and silicon (111) substrates. Substrate temperature is varied from 35 °C to 450 °C. The gas mixture for sputtering is inert argon (Ar) and reactive nitrogen (N2). Total pressure of sputtering gas mixture is kept constant at 12 mTorr but partial pressures of Ar and N2 are varied. Ar partial pressure to total pressure ratio is varied from 0 to 0.75. Optical bandgap values from 1.4 eV to 3.15 eV, absorption coefficient values of ∼104 cm−1 to ∼7 × 105 cm−1 and critical film thickness values of 0.04 μm to 4 μm are measured. UV–visible spectroscopy method and Tauc plots are used. Bandgap tuning with Ar partial pressure ratio and substrate temperature is presented.