Impact of deposition temperature on crystalline quality, oxygen vacancy, defect modulations and hetero-interfacial properties of RF sputtered deposited Ga2O3 thin films on Si substrate

Abstract

In the current work, thin film (∼55 nm) of n-type Ga2O3 (n-Ga2O3) is deposited on silicon (p-Si) substrate by using radio-frequency (RF) sputtering technique with systematic substrate temperature variations (room temperature to 700 °C). The structural, optical properties and chemical states of elements of the deposited films are observed to depend significantly on the deposition temperatures. The chemical composition and oxidation states, optical properties, defect states and structural quality of the deposited films are investigated in detail by employing x-ray photoelectron spectroscopy, energy dispersive x-ray, spectroscopic ellipsometry, Raman, photoluminescence and atomic force microscopy images. X-ray diffraction result reveals a polycrystalline nature of monoclinic β-phase of Ga2O3 with (403) dominant plane. The work functions are calculated from the ultraviolet photo-electron spectroscopy for all the deposited films and Ga2O3/Si heterojunction properties are investigated by using current–voltage (I–V) and capacitance–voltage (C–V) measurements. Among all the fabricated heterojunctions, 600 °C deposited Ga2O3 film exhibits superior performance in terms of energy bandgap, work function, refractive index, barrier height, rectification ratio and effective carrier concentrations. The current transport mechanism is analysed using the appropriate energy band diagram of Ga2O3 and Si. Therefore, the study suggests that 600 °C deposition temperatures is the optimum temperature for developing a high quality Ga2O3 thin film on Si by using RF sputtering technique and corresponding Ga2O3 thin film/Si heterojunction can be a potential candidate for developing several electronic and optoelectronic devices.