Research On The Performance Of Ga₂O₃ And Its Heterojunction Photodetectors

Ga₂O₃ is a direct band gap semiconductor material with both good thermal stability and excellent chemical stability.Its forbidden band width covers a photon energy range from 4.2e V to 5.3 e V and is considered an ideal material for the manufacture of solar-blind photodetectors.Although Ga₂O₃ itself has excellent electrical and optical properties,Ga₂O₃-based photodetectors still have the following issues that need attention:（1）The development of Ga₂O₃ photodetectors is currently limited by the quality of amorphous Ga₂O₃ films,and the deposition process of Ga₂O₃ films needs to be optimised to improve the quality of Ga₂O₃films.（2）β-Ga₂O₃ is an ideal material for preparing solar-blind ideal material for wavelength band detectors,but due to the inherent defects of its preparation method,it makes the preparedβ-Ga₂O₃ crystals of poor quality and low responsiveness,which is difficult to meet the needs of practical applications.Therefore,new preparation methods and techniques need to be explored to improve the purity and quality ofβ-Ga₂O₃.According to the needs of practical applications,this thesis aims to improve the performance of Ga₂O₃ photodetectors by optimising the quality of amorphous Ga₂O₃ films,innovating the growth method ofβ-Ga₂O₃,constructing Ga₂O₃/PDPP3T:PC₆₁BM heterojunctions and other methods to effectively improve the performance of the devices,and systematically analysing the mechanism of performance improvement,the main research results are as follows:（1）Aiming at the problem of more defects on the surface of amorphous Ga₂O₃ films,this study has successfully optimised the quality of amorphous Ga₂O₃ films and improved their photodetection performance by adjusting the deposition parameters from the perspective of improving the preparation process of amorphous Ga₂O₃ films.The Ga₂O₃/Au photodetectors were successfully prepared by photolithography and wet etching processes,and the influence of the film quality on the photodetector performance under different preparation conditions was investigated.The results show that the response of Ga₂O₃photodetectors in the day-blind region is improved from 0.06 A/W to 0.40 A/W at 140 W and0.5 Pa.This study provides reliable experimental support for the performance improvement of Ga₂O₃ photodetectors.（2）β-Ga₂O₃ is an effective solution to the problems of poor stability,low light-to-dark ratio and high noise of amorphous Ga₂O₃ films,but its relatively harsh preparation conditions and poor crystal quality still limit its widespread application in industrialization.Based on the above problems,this study proposes a novel method for the growth of gallium oxide microwires（β-Ga₂O₃ MWs）and investigates the mechanism of this growth method.The method uses gallium（Ga）as the reaction source and is capable of growingβ-Ga₂O₃ MWs in situ on substrates under the combined effect of Vapour-Solid（VS）and Vapour-Liquid-Solid（VLS）growth mechanisms.Theβ-Ga₂O₃ MW photodetector has the advantages of lower preparation cost,simpler process and more stable crystal properties than the amorphous thin-film structured Ga₂O₃ photodetector,while the overall responsivity reaches about 0.7 A/W,with a day-blind-to-visible suppression ratio of 2 orders of magnitude and a light-to-dark current ratio of 3 orders of magnitude.β-Ga₂O₃ MW with superior crystal quality,a narrower cut-off edge（262 nm）,a higher EQE（367%）and a higher detection rate(4×10¹¹ Jones)than those prepared by conventional growth methods.（3）From the perspective of constructing heterojunctions,the Ga₂O₃/PDPP3T:PC₆₁BM thin film heterojunction photodetector and theβ-Ga₂O₃MW/PDPP3T:PC₆₁BM heterojunction photodetector were constructed by spin-coating PDPP3T:PC₆₁BM thin film on the surface of the prepared Ga₂O₃ thin film photodetector andβ-Ga₂O₃ MW photodetector respectively.This enables the optimization of the performance of Ga₂O₃ photodetectors and the realization of multi-band detection to expand their application range.The analysis shows that PDPP3T:PC₆₁BM has good crystallisation properties on both device surfaces and excellent absorption properties in the IR band.Theβ-Ga₂O₃MW/PDPP3T:PC₆₁BM heterojunction photodetector has an increase in maximum photocurrent of about three orders of magnitude compared to the thin-film heterojunction photodetector,and exhibits excellent detection capability in all wavelengths,with a maximum response of 0.61 A/W in the UV band and 3.33 A/W in the IR band.