Electrical and optical properties of transparent conducting In_xGa_1−xN alloy films deposited by reactive co-sputtering of GaAs and indium

Thin films of In_xGa_1–xN alloys were deposited by reactive sputtering using a GaAs target, covered partially with indium and co-sputtered with nitrogen. X-ray and electron diffraction studies indicate the formation of single phase In_xGa_1–xN films at ∼ 500 °C. Hall effect and resistivity measurements show that the alloy films with x ≥ 0.5 have high carrier concentrations in the range of 10²⁰–10²¹ cm⁻³ and mobility of ∼ 10 cm² V⁻¹ s⁻¹. Optical measurements of the alloy films show a strong dependence of the band gap on carrier concentration, which is attributed to the Burstein–Moss shift and free carrier effects in the near-infrared region. The values of electron effective mass obtained from plasma resonance data and the Burstein–Moss shift show good agreement. Over a limited composition window of x in the range of 0.5–0.6, the alloy films exhibit low electrical resistivity (≈ 10⁻³ Ω-cm) and high transparency in part of the visible and near infrared regions, followed by high reflectance in the infrared region, which show their potential for applications as transparent electrodes in photovoltaic and photonic devices and as heat mirrors. - Highlights: • In_xGa_1–xN alloy films were deposited by co-sputtering of GaAs and In with 100% N₂. • Films deposited at ∼ 500 °C are polycrystalline single phase hexagonal In_xGa_1–xN. • In_xGa_1–xN alloy films with x > 0.5 exhibit a low resistivity of ∼ 10⁻⁵ Ω-m. • Alloy films exhibit ∼ 80% transmittance in the wavelength range of 500–1500 nm. • Band gap and effective mass of alloy films depend on free electron concentration