Research On Rare Earth Metal Oxide Ultraviolet Detector

Ultraviolet photodetectors are photoelectric devices that convert absorbed ultraviolet light energy into current or voltage,and these devices have been widely used in missile warning,detection of ozone hole areas in the atmosphere,safety monitoring of high-voltage power transmission and transformation equipment,wireless communication,and other fields.Due to the fact that ultraviolet light in the shortwave band of sunlight is absorbed by particles,ozone,and water vapor in the air and does not exist near the earth’s surface,short wave ultraviolet detectors can continue to operate without being affected by sunlight compared to medium and long wave ultraviolet detectors.Shortwave ultraviolet detectors often have higher sensitivity and lower false alarm rates,so the research on shortwave ultraviolet detectors has also received increasing attention.Currently,shortwave ultraviolet detectors are mostly made based on broadband gap semiconductors such as AlGaN,MgZnO,and Ga₂O₃.Short wave ultraviolet detectors based on these wide band gap metal oxide semiconductors have many advantages.For example,photodetectors made of metal oxides are not easy to oxidize and exhibit sensitive responses.Moreover,they can be more easily made into small sized devices,which is conducive to device integration.Therefore,broadband gap metal oxide semiconductors and shortwave ultraviolet detectors fabricated from them have received considerable attention in recent years.Currently,the main problems with wide band gap semiconductors are short carrier and exciton lifetimes,and internal defects in materials,etc.which will make it difficult for the devices fabricated from a single material to have high performance.Therefore,preparing high-performance ultraviolet detectors from composite materials has become a choice.In this thesis,the sol-gel method is used to fabricate short wave ultraviolet detector based on the rare earth metal oxide Nd₂O₃.The fabrication process of the detector is the sol-gel method.Although the manufacturing process of the detector is simple and the cost is low,the performance of the fabricated device is excellent.Devices fabricated using a single rare earth metal oxide have a dark current of only 1.66×10^-11 A when subjected to a bias voltage of 5 V.Its photocurrent reaches 2.21×10^-8 A at a bias voltage of 5 V when irradiated with 280 nm light with a light intensity of 15μW/cm².The light dark suppression ratio under this condition is 1.33×10³,reaching three orders of magnitude.Compared with some short-wave photodetectors published in recent years,devices based on rare metal oxide fabricated in this thesis have relatively excellent performance,especially in the dark current performance indicator,leading the ranks.This allows the device to meet the detection needs while having a lower standby power consumption,thereby improving energy utilization,avoiding resource waste,and taking a small step forward on the road to energy conservation and environmental protection.Secondly,an ultraviolet photodetector based on Nd₂O₃/TiO₂ heterojunction was fabricated,which promotes exciton separation and prolongs recombination time by forming a built-in electric field in the heterojunction,thereby increasing the device’s photocurrent.When a device based on Nd₂O₃/TiO₂ heterojunction is subjected to a bias voltage of 5V under 280 nm light irradiation with a light intensity of 15μW/cm²,its photocurrent is 4.12×10^-6 A,with a light to dark suppression ratio of 2.75×10³.Compared to the photocurrent of devices fabricated from a single Nd₂O₃ under the same test conditions,its photocurrent has been increased by two orders of magnitude,and the light to dark suppression ratio has been doubled.The corresponding responsiveness（R）and detection rate（D*）values have been improved,and the response recovery time has also been shortened greatly.In summary,it can be seen that the rare earth metal oxide Nd₂O₃ is expected to be used for the production of ultra-high performance solar blind ultraviolet detectors.