Research On Ga₂O₃ Heterojunction And Au Nanoparticle Composite Enhanced UV Detectors

In recent years, ?-Ga2O3, as a new type of wide and direct bandgap semiconductor, exhibits great application prospect in solar-blind photodetector, gas sensor, information storage, field effect transistor and so on. Especially in photodetector area, gallium oxide has received wide attention all over the world and achieved great development. Our group has also done a lot of research on gallium oxide based solar blind UV photodectors. Although researchers have made great progress in the field of gallium oxide, the existing performance still needs to be improved. In this paper, we mainly focus on how to optimize the performance of gallium oxide UV photodetectors through various experiment methods.We have systematacially studied the influence of film thickness,microstructure, surface plasmons and Ga2O3 based heterojunction. The detailed works are shown as follows:(1) The relationship between the photodetector property and film parameter (such as the thickness and the grain size in Ga2O3 film) was investigated. (201) oriented ?-Ga2O3 films were deposited on sapphire substrate. With the film thickness increase, the crystal grain size increase,absorption peak behaves blue shift, band gap increase and the dark current decrease correspondingly. The thickness of about 200 nm for the?-Ga2O3 thin film based photodetector exhibit better photoresponse, faster rise time and fall time.(2) Hybrid Au nanoparticle/?-Ga2O3 thin film were fabricated. We obtain dual-band dual channel detector with 254 nm and 532 nm dual channel response by introduce surface plasmons. By the plasma resonance behavior of Au nanoparticles on ?-Ga2O3 film, the photoresponsivity of the detector are improved obviously. With increasing size and particle concentration of Au nanoparticle, the detector shows lower dark current, larger light current, higher photoresponse and faster switching time. Afterwards, the carrier transport mechanism is explained properly in our research.(3) The n-SiC/n-Ga2O3 and p-Si/i-SiC/n-Ga2O3 heterojunction photodetectors were fabricated. The oxygen vacancy concentration of?-Ga2O3 thin film is reduced through annealing in oxygen atmosphere,which improves the photodetector rectifying property, photoresponse time and sensitivity. The photoresponsivity of n-n and p-i-n heterojunction increase to 6308.0% and 5.4 × 105% respectively.Moreover, the heterojunction is completely unresponsive to 365 nm illumination. Due to inserting SiC layer as an electron blocking layer, the rectification direction of photodetectors are changed, the leakage currents are largely decreased, the rectification ratio are increased as well. Finally,the carrier transport mechanism of the heterojunction is also explained properly.