Growth and characterization of gallium oxide thin film based solar-blind photdetector

Abstract

Solar-blind photodetectors (PDs) are an emerging technology for forest fires, territory intrusions, ozone hole monitoring, deep space exploration, satellites, and security communication. A photodetector working in <280 nm with a suitable optical band gap, solar-blind region, could minimize the chances of false radiation detection even under intense sun interference on the earth’s surface by detecting the ozone layer filtered deep UV (UV-C) terrestrial signatures. So far, solar-blind photodetectors based on ZnMgO, ZnGa2O4, Zn2GeO4, AlxGa1−xN, In2Ge2O7, and LaAlO3 materials are realized by using band-gap tuning through the alloying process and optimizing their performance in the solar-blind region. However, the process of alloying makes the fabrication complex and introduces high defect density, thereby increasing the dark current and limiting the performance of solar-blind photodetectors especially in self-powered mode. Alternatively, β-Ga2O3 is considered a strong candidature of working at the solar-blind region due to its intrinsically solar-blind nature without the necessity of the alloying process, superior physical properties and chemical stability. However, detectors based on β- Ga2O3 have very low optoelectronic performance and hence cannot be used for any practical applications. A detailed investigation to correlate the growth parameters-optoelectronic properties-device performance is required to realize any practical application of gallium oxide thin film based solar-blind photodetectors. In this work, we explore the challenging issues and traced developments in Ga2O3 based solar-blind photodetectors and finally deliver solutions for significant improvements in the performance for a more efficient and reliable practical application. In response to the challenges, one of the objectives of this work is the growth of high-quality, high-performance and self-powered Ga2O3 thin-film based UVC PDs on cost- effective Si substrate with various optimized parameters. The results revealed that samples grown on the high-temperature seed layer and with various optimized parameters exhibit excellent crystalline quality and optoelectronic performance which is largest amongst the planar β-Ga2O3 PDs. The zero-bias digitizing sensor prototype produces a digitized output bit with deep UV (DUV) light that exhibits a high on/off (I254 nm/Idark) ratio of >103, a record-low dark current, and high stability and reproducibility over 100 cycles even after >10,000 hrs. In this work, we also report on the performance of a thin film of gallium oxide decorated with Ag plasmonic nanoparticles, which surprisingly, exhibits a change in the polarity of the photocurrent for UV-A and UV- C bands. The device showed very high responsivity in the UV-A and UV-C bands. This plasmon-enhanced solar-blind gallium oxide photodetector allows UV regions to be spectrally distinguished, which is useful for the development of sensitive dynamic imaging photodetectors. The goals of this thesis was met by the fabrication of gallium oxide based solar-blind photodetectors, that were fabricated on cost-effective and flexible substrates for next-generation wearable and flexible electronics. In contrast to the traditional design of PDs, we report a facile and unique hand-sketched bottom asymmetric electrodes based disposable, eco- sustainable, light-weight, ultra-flexible and cost-effective paper-based a-Ga2O3 thin film PD.