Research On Device Technology Of Mixed Structure MgZnO Solar Blind Ultraviolet Detector

Ultraviolet solar blind detectors could be widely used in missile early warning,flame detection,and so on.In recent years,thin film semiconductor materials are often used as materials for solar blind detectors due to their advantages in volume and power consumption,such as Ga₂O₃,Al Ga N,Si C,etc.MgZnO has relatively high responsivity and wide detectable ultraviolet range.In addition,MgZnO can be made at relative lower growth temperature,which makes MgZnO as an ideal material for making solar blind ultraviolet detectors.According to related researches in recent years,although MgZnO solar blind detectors have shown relative higher performance,there are still small numbers of research that focused on the fabrication technologies of MgZnO UV detectors.It is reported that the plasma enhancement effect of metal nanoparticles can improve the responsivity and signal-to-noise ratio of ultraviolet detectors,and some studies show that Ag nanoparticles have enhancement effect on MgZnO solar blind detectors,but there are less researches on the preparation technology of Ag nanoparticles.Therefore,in this paper,the modification technology of Ag nanoparticles and the preparation technology of electrodes would be optimized.Ag nanoparticles would be prepared by spin coating method,and the performance of Ag nanoparticles plasma enhanced mixed phase MgZnO solar blind UV detector was studied.In order to eliminate the influence of etching solution on MgZnO thin film during lithography,lift-off lithography process was used as electrode fabrication technology of MgZnO UV detectors.At the same time,Ag and Al metals are also used as electrodes in MgZnO solar blind UV detector,and the effect of different electrode fabrication technologies and different metal electrodes on the performance of MgZnO UV detector would be studied.The main research contents and results of this paper are listed as follows:1.Dense Ag nanoparticles with a diameter of 30nm were prepared by spin coating method,and Ag nanoparticles were modified on MgZnO thin films.MgZnO UV detectors were prepared by photolithographic process,and the effects of different spin coating speeds on the performance of MgZnO solar blind UV detectors modified by Ag nanoparticles were investigated.It was found that the dense Ag nanoparticles with a diameter of 30 nm greatly enhanced the MgZnO solar blind UV detector.The responsivity of the device reached 4.48A/W at 240nm,which was 90 times that of the unmodified device;the dark current was 25V.Under the bias voltage of only 3.78n A,there is not much difference compared with unmodified devices;and its maximum light dark current ratio reached 3.85×10⁵,which was nearly 3 orders of magnitude higher than that of the device without modification of Ag nanoparticles.2.A complete lift-off lithography process is explored,and the influence of electrodes prepared by wet lithography process and lift-off lithography process on the device performance of MgZnO solar blind UV detector is studied.Since the lift-off lithography process avoids the influence of metal etching solution on the device,the detector device using the lift-off lithography process to prepare the electrode has a maximum response of 2.85 A/W at 235 nm,a maximum response of 4.9 A/W at about 290 nm in the near ultraviolet region,a19-fold increase in the response of the device at 235 nm in the deep ultraviolet region and a13.6-fold increase in the near ultraviolet region,and the maximum light dark current ratio of the device reaches 2735,which is an order of magnitude higher than that of the wet lithography sample.3.MgZnO detector modified by Ag electrode and MgZnO detector modified by Al electrode were prepared by lift-off photolithographic process,and the effects of different metal electrodes on the device performance of MgZnO solar blind UV detector were studied.Due to the low barrier height between Ag and MgZnO thin films,the MgZnO solar blind UV detector using Ag metal electrode has a large internal gain effect under UV irradiation.The response of MgZnO solar blind UV detector modified by Ag electrode at 260 nm reaches 14A/W,which is 2.86 times higher than that of device modified by Au electrode,and the dark current ratio of light at 25 V bias voltage reaches 1417,which is about 7.6 times higher than that of device modified by Au electrode under the same voltage.Although the barrier height between Al and MgZnO is also relatively low,the performance of the device modified by Al electrode decreases greatly due to the inevitable oxide layer generated during the preparation process.