Research On Solar-blind Ultraviolet Detection Properties Of Gallium Oxide/Zinc Oxide Heterojunction Under Multi-Physical Fields Modulation

Solar-blind ultraviolet（UV）photodetectors（PDs）have the advantages of strong anti-interference ability and low false alarm rate,and have been widely used in military and civilian fields such as missile tracking,secure communication,environmental monitoring and biometric identification.Gallium oxide（Ga₂O₃）is considered as an ideal material for solar-blind UV PDs due to its suitable band gap（4.4～5.3 e V）and excellent thermal and chemical stability.At present,solar-blind UV PDs based on Ga₂O₃ mainly include photoconductive type and self-powered type.Among them,the photoconductive PD is simple in structure and easy to prepare,but it has the problems of large dark current and slow response speed.Self-powered PD have the advantages of low dark current,fast response speed and low power consumption,but the responsivity is usually low.In view of the problems of photoconductive type and self-powered type Ga₂O₃ PDs,ZnO and Ga₂O₃ films heterojunction are constructed by magnetron sputtering and pulsed laser deposition methods in this paper.The separation,transport and recombination behaviors of photogenerated carriers near the heterointerface are modulated by multiple physical fields（built-in electric field,piezoelectric field,ferroelectric depolarization field）,and the performance of the Ga₂O₃solar-blind PDs is optimized and improved,the main achievements are as follows:（1）Research on modulation of Ga₂O₃/ZnO photodetectors by built-in electric field.ZnO and Ga₂O₃ films were grown by magnetron sputtering and pulsed laser deposition methods,and sandwich structure(Ga₂O₃/Au electrode/ZnO photoconductive detectors were fabricated.The effects of surface defects and crystal quality of Ga₂O₃ films and the interfacial built-in electric field on the dark current of the devices were investigated by X-ray diffraction,photoluminescence spectra and fluorescence lifetime.The relationship between the photoresponse characteristics of sandwich structure detectors and the device structure is studied.Based on the energy band model,the mechanism of the high gain of the detector is analyzed.The high gain is attributed to the transfer of photogenerated holes from the valence band of Ga₂O₃ to the valence band of ZnO driven by the interfacial built-in electric field and the increase of hole mobility in ZnO.At 10 V bias,the responsivity and detectivity of the sandwich structure detector to 255 nm solar-blind UV light reach 336.3 A/W and 10¹⁵ Jones,and the gain is 1637,which is 1443 times higher than that of Ga₂O₃ single-layer film device.（2）Research on modulation of Ga₂O₃/ZnO photodetectors by piezoelectric field.ZnO and Ga₂O₃ films were grown by magnetron sputtering method,and photoconductive type and self-powered type Ga₂O₃/ZnO PDs were prepared.Combined with current-voltage（I-V）and current-time（I-t）characteristic curves,the effects of piezoelectric field generated in ZnO on the performance of the two detectors were studied.According to the piezoelectric effect theory,the modulation effects of piezoelectric field on the energy band bending,photogenerated carriers separation,transport and recombination behaviors of Au/Ga₂O₃ and Ga₂O₃/ZnO interface are investigated.In the photoconductive device,the height and width of the barrier at the Au/Ga₂O₃ interface are modulated by the piezoelectric field.At 20 V bias,the responsivity and detectivity of the device to 254 nm solar-blind UV light reach 2.5 A/W and 10¹⁴ Jones,which are 3.8 times and 6.2 times higher than that of the original device.In the self-powered device,the energy barrier difference of Ga₂O₃/ZnO interface is modulated by the piezoelectric field.At 0 V bias,the responsivity of the device to 254 nm solar-blind UV light reaches 2.7m A/W,which is 1.5 times higher than that of the original device.（3）Research on modulation of Ga₂O₃/ZnO:V photodetectors by ferroelectric depolarization field.ZnO:V and Ga₂O₃ films were grown by pulsed laser deposition method,and self-powered Ga₂O₃/ZnO:V PDs were constructed.Combined with current-voltage（I-V）and voltage-time（V-t）characteristic curves,the effect of ferroelectric depolarization field generated in ZnO:V on the detector performance was studied.According to the interfacial energy band theory,the modulation effects of ferroelectric depolarization field on the energy band bending,photogenerated carriers separation and transport behaviors of Ga₂O₃/ZnO:V interface are studied.The intensity of the built-in field and the width of the depletion region at the Ga₂O₃/ZnO:V interface are modulated by the ferroelectric depolarization field.At 0 V bias,the responsivity of the device to 260 nm solar-blind UV light reaches 95.5 m A/W,which is3.2 times higher than that of the original device.