The Fabrication Of MgZnO Ultraviolet Detector With High Signal-to-noise Ratio And The Study On Characteristics Of The UV Detector Responsivity

Ultraviolet?UV?detectors have a broad prospect in military and civilian applications.The current researches on UV detectors are mostly prepared on the wide bandgap semiconductor materials such as diamond,SiC,GaN,and Ga₂O₃.Compared to these materials,ZnO and its alloy MgZnO have many advantages.For example,there is matched single crystal substrates for growth of high quality MgZnO thin films,the band gap of MgZnO could be tuned form 3.37eV to 7.8eV,the preparation and processing technology of MgZnO are relatively simple,MgZnO is a rich and environment-friendly materials.In this paper,MgZnO films with different hexagonal MgZnO/cubic MgZnO ratios were deposited by pulsed laser deposition?PLD?method through the change in both the Mg content of MgZnO targets and the growth conditions.The effect of different hexagonal MgZnO/cubic MgZnO ratio in MgZnO thin film on its UV response characteristics was studied.In addition,Ag nanoparticles are introduced into the MgZnO UV detector,which is a possible method to improve the UV response of the MgZnO UV detector.The main research contents and results of this paper are as follows:1.MgZnO films with different Mg contents were grown on quartz and MgO substrates using MgZnO targets with different Mg contents.The Mg content in MgZnO films grown on both quartz and MgO substrates increased with Mg content in the MgZnO target.When the Mg content increased,the crystal structure of MgZnO thin film grown changed from hexagonal structure to mixed structure on fused quartz substrate.The crystal structure of MgZnO thin film grown changed from mixed structure to cubic structure on cubic MgO substrate.The peak responsivity of the MgZnO UV detectors on quartz and MgO substrates both decreased when the Mg content increased,and the wavelength position for the maximum response of the device makes blue shifts.At the bias of 25V,the I_300nm/I_dark of the Mg_0.40Zn_0.60O UV detector on fused quartz substrate reached 100;the response of the Mg_0.21Zn_0.79O UV detector on MgO substrate at 240 nm deep UV light reached 6.81 A/W,which corresponding to 3519%quantum efficiency of the device.The response of the MgZnO UV detector on MgO/fused quartz substrate at 240 nm deep UV Light reached 11.46A/W,which corresponding to 5921%quantum efficiency of the device.2.MgZnO thin films with different cubic/hexagonal structure ratios were fabricated on the quartz substrate through simultaneously adjustment of the growth temperature and oxygen pressure with the same Mg_0.4Zn_0.6O target.The MgZnO thin films grown along cubic structure under both lower temperature and oxygen pressure condition,and the MgZnO thin films grown along both cubic and hexagonal structures under both higher temperature and oxygen pressure condition.The mix-structure MgZnO based UV detector had two response peaks,,and the I_300nm/I_dark of the MgZnO UV detectors reached more than 100 at 25V bias voltage.3.MgZnO UV detector without Ag nanoparticles was fabricated,and the Ag nanoparticles was induced through vacuum anneal of Ag thin film on the surface of the device.Under 5V bias voltage,the responsivity of the Mg ZnO UV detector with the Ag nanoparticles at 330 nm is 2.75 times the detector without Ag nanoparticle.And because the I_dark of the MgZnO UV detector with Ag nanoparticles decreased,the I_light/I_dark of the MgZnO UV detector with Ag nanoparticles is 11.3 times the detector without Ag nanoparticles at25V bias voltage.