Fabrication and characterization of Ga2O3/p-Si P-N hetero junction UV photodetectors

Ultra-wide band gap (Ga2O3) has attracted much attention in recent years due to its chemical and thermal stability and various potential applications for devices used in opto-electronics and power electronics. Solution-based synthesis is a simple and cost-effective synthesis method that provides high efficiency at low temperatures. In this thesis study, n-β-Ga2O3 thin films were coated on p-Si substrates by sol-gel spin-coating method. n-Ga2O3:X/p-Si (X: W+4, Ti+4, Sb+4, Zn+2, Sn+4) UV solar- blind photodetectors (SBPD) were produced by using doped and undoped β-Ga2O3 thin films. The effect of the type and ratio of dopants on the optical, atomic, surface morphologies and electrical properties of the photodetector (PD) was investigated. In these researches, X-ray diffraction spectra (XRD), scanning electron microscopy (SEM) analyses, and UV-Vis spectroscopy measurements were used. Electrical characterization of the produced photodetectors was investigated by current-voltage (I-v) measurements. Ga2O3 has been successfully synthesized by the solution synthesis method with gallium (III) nitrate hydrate used as the gallium source. With the subsequent thermal annealing process, improvements were observed in the ratio of Ga element and O element in the Ga2O3 compound, while a transformation to β-Ga2O3 phase was observed, especially at high temperatures. UV-Vis analyzes showed that doped and undoped β-Ga2O3 thin films of the same thickness exhibited similar transmittance spectra. It has been shown that reduced transmittance films in the deep ultraviolet region below 280 nm can be used as a SBPD emitter layer. To investigate the optoelectronic performance of doped and undoped β-Ga2O3 devices, current-voltage (I-v) measurements were carried out in the dark and under light. To comprehend SBPD behavior, the heterojunction occurring between n-β-Ga2O3 and p-Si was qualitatively examined through realignment of band positions under reversed bias. The results showed that with doping, the photocurrent increased simultaneously under the forward and reverse feed region, and the junction quality in n-β-Ga2O3/p-Si heterojunctions became better after the addition of dopants. Temporal response measurements revealed that the response of the doped n-β-Ga2O3/p-Si p-n heterojunction based photodetector varies depending on the type of dopant. The response time improvement has been attributed to the rapid separation and migration of photoexcited carriers due to suppression of defect states or the strong p–n junction that can efficiently separate photoexcited carriers. The results of this study demonstrate that it will provide a way to fabricate simple, low-cost, and high-performance β-Ga2O3 solar-blind photodetectors.