Unveiling structural and optical properties of Sn-doped β-Ga2O3: A correlation of experimental and theoretical observations

This work presents the experimental and theoretical insights into the structural and optical properties of tin (Sn)-doped β-Ga2O3. Sn-doped β-Ga2O3 films were fabricated using the low-pressure chemical vapor deposition (LPCVD) method onto the c-plane sapphire substrate. Further, deposited thin films were characterized for their structural and optical properties. XRD pattern depicts the crystalline nature of β-Ga2O3. The energy band gap (Eg) obtained from UV–Vis spectra has been decreased from 4.82 eV to 4.77 eV for as-deposited β-Ga2O3 to Sn-doped β-Ga2O3, respectively. However, an increase in absorbance has been observed in Sn-doped β-Ga2O3 films. Further, the first principle study based on density functional theory (DFT) has been used to comprehend the effect of Sn doping in β-Ga2O3 films. DFT result reveals the expansion of the lattice parameter of intrinsic β-Ga2O3 on the introduction of the Sn atom. Furthermore, a reduction in Eg has been observed upon Sn doping into the β-Ga2O3 structure similar to the experimental results. The reason behind the reduction in the Eg may be due to the Sn-5s energy level at the bottom of the conduction band as revealed in density of state (DOS) investigations. Also, the DOS results of Sn-doped β-Ga2O3 suggest that the atom has tended to form the ionic bond characteristics with the introduction of Sn into the β-Ga2O3, where the free electrons of the Sn-5s orbital state will fill the conduction band and may improve the conductivity. Additionally, optical properties such as reflectance and dielectric loss of function have been investigated. The reflectance and dielectric loss of function result proposed that more energy was absorbed when Sn was introduced to β-Ga2O3. Therefore, our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices. Novelty statement β-Ga2O3 is an emerging material for optoelectronic device applications due to its excellent wide energy band gap, high critical electric field strength, high melting point, high Baliga figure of merits (BFOM), and exceptional physical and chemical stability. However, intrinsic β-Ga2O3 suffers from poor mobility and surface defects. Therefore, β-Ga2O3 needs a dopant material to enhance its' structural and optical properties. In this case, Sn doping may improve the optoelectronic properties of β-Ga2O3. Therefore, detailed theoretical and experimental investigations on Sn-doped β-Ga2O3 become necessary to understand inside phenomena. However, lots of experimental and theoretical works have been performed on Sn-doped β-Ga2O3. But, to date, there is no available report related to the correlation of theoretical and experimental data-based studies on Sn-doped β-Ga2O3. In this work, we have explored the structural and optical properties of Sn-doped β-Ga2O3 thin films deposited by the LPCVD method on the c-plane sapphire substrate. Further, the experimental results obtained were correlated with the first principal based DFT results. Our observation suggests that upon Sn doping into β-Ga2O3, optical as well as structural properties were improved and these improved properties may be useful for optoelectronic devices.