Fabrication Of The ?-Ga₂O₃-Based Ultraviolet Detector And Its Photoelectric Properties Measurement

Gallium oxide?Ga₂O₃?,with a band gap of 4.9 eV,is a wide band gap semiconductor material.It has aroused increasing interest in researchers due to high thermal stability and chemical stability,large band gap,strong resistance to breakage,excellent UV transmittance.Owing to its suitable band gap,the corresponding wavelength is 253 nm,Ga₂O₃is an ideal material for solar blind UV detector.However,there are a lot of problems about Ga₂O₃ detector,such as defects like oxygen vacancy,high resistance leading to the weak signals of the detector,large size,low gain and can't detect the level of single photon.In this paper,the application of ?-Ga₂O₃ in optoelectronic devices has been studied.The work in detail is presented as follows:1.A simple MSM?Metal-Semiconductor-Metal??-Ga₂O₃ UV detector was fabricated by using L-MBE and magnetron sputtering.The DC optoelectronic properties were measured by using the Kethley 4200 low noise test system with precision of 10-15 A,the response time parameters were quantitatively analyzed by double exponential curve fitting.The dark current of the photo detector is about 0.4 nA at 10 V bias and hardly responding to 365 nm UV light.While illuminated by 254 nm,the current increases rapidly to 15 nA,the photo-dark ratio is about37.5,the reponsivity is 0.0119 A/W,external quantum efficiency is 5.46%.The response time is?r1 = 3.39 s,?r2 = 20.30 s,?d1 = 0.6 s,and ?d2 = 16.69 s.In addition,labview simulation is used to verify the feasibility of the lock-in amplifier system to measure weak AC signals.Finally,a lock-in amplification test system is built and the AC performance of the detector is measured.At1 V?5 Hz?bias voltage,the dark current is 15 nA,and when illuminated by 254 nm,the photocurrent is 75-80 nA.2.By Zn doping,the oxygen vacancy of the ?-Ga₂O₃-based detector can be reduced and the photoelectric performance was improved,such as photo-dark ratio,the reponsivity,the external quantum efficiency,and the photo response time.Compared with the pure ?-Ga₂O₃,the photo-dark ratio increased from 37.5 to 74.4,the reponsivity increased to 0.032A/W,the external quantum efficiency increased to 15.99.The response time ?r1 = 3.39 s to 1.95 s,?r2 = 20.30 s to15.04 s,and the decaying process was reduced to one process ?d = 0.25 s.The electrode wasprepared by UV lithography,which made the electrode smaller.The photo-dark ratio and the photo response time is similar but the reponsivity and external quantum efficiency have hugely increased to 0.374A/W and 182%,respectively,Which laid the foundation for fabricating the array of the detector.The thin-film chip was packaged and the external circuit including detection circuit and alarm circuit was designed,making the detector more compact and portable.3.The ?-Ga₂O₃ / p-Si PN junction was fabricated on p-Si substrates.The PN junctions were operated in a linear mode by reverse bias.The gain,photoelectric properties and linearity were measured.I-t Curve was fitted and the CV curve measured by using the Kethley 4200 low noise test system.Both have proved that the response time decreases with increasing bias voltage.At a low reverse bias voltage of 3V,the gain of the detector reaches 105,the photoresponse at unity gain is 0.082 A / W,the external quantum efficiency is 40.03%,and ?r1 at the bias voltage of 0.5V,1V,2V,3V was 2.21 s,1.59 s,1.23 s,1.15 s,respectively.?d1 at bias voltages of 0.5V,1V,2V and3 V was 2.2 s,1.65 s,1.21 s and 1.15 s,respectively,while ?r2 and ?d2 were stable at 20 s.Finally,since the ?-Ga₂O₃ detector is currently unable to operated in the Geiger mode,the near-infrared single photon detector InGaAs / InP is used to measuring in Geiger mode.We use the passive quenching circuit to capture the dark counts on the oscilloscope,The sinusoidal gating mode was using to measure the important performance parameters such as dark counts rate and single photon detection efficiency,which lays the foundation for the future work of the solar blind single photon detection.At the best excess bias voltage of 3V,the dark count rate is 6.67 × 104 / s and the single photon detection efficiency is 25.76%.