Research On High Performance Ultra-Wide Bandgap Gallium Oxide Solar-Blind Ultraviolet Detector

In August 2022,the Bureau of Industry and Security of the US Department of Commerce issued an announcement listing a series of technologies including gallium oxide（Ga₂O₃）,an ultra-wide bandgap material,as new export control items,which caused further decoupling between China and the US in the semiconductor field.The reason why Ga₂O₃ has such an important strategic significance is mainly attributed to its excellent material properties.Compared with the first-generation semiconductor Si and Ge,the second-generation semiconductor In P and Ga As,and the third-generation semiconductor Si C and Ga N,the fourth-generation semiconductor Ga₂O₃ has a wider bandgap（4.6～4.9 e V）and ultra-high critical breakdown field strength（8 MV/cm）.In addition,the single crystal substrate of Ga₂O₃ can be obtained by a melting method,which can greatly reduce the cost of the material,which is also the key to achieve commercial mass production of Ga₂O₃ and its related devices.At the same time,the ultra-wide bandgap also makes the light absorption cutoff edge of Ga₂O₃ material lie in the range of solar-blind ultraviolet（UV）zone which is below 280 nm,thus the front optical filter is not needed.In addition,Ga₂O₃ also has a high light absorption coefficient,radiation resistance and many other advantages,which indicate that Ga₂O₃ is an ideal material for the detection of solar-blind UV light.Ga₂O₃ solar-blind UV detector has very broad application prospect in military and civil fields.It can be applied to the missile approximation warning system.It has some advantages,such as low false alarm rate,small size,light weight and high sensitivity.At the same time,it can be used for automobile exhaust monitoring,fire monitoring,imaging and other fields.Based on the above reasons,this article improves the detection performance of Ga₂O₃ solar-blind UV detector from the aspects of improving material quality,optimizing device structure and improving manufacturing process.At the same time,the application of Ga₂O₃solar-blind UV detector in the field of communication was preliminarily explored.The specific research results are as follows:1.Based on the material growth method of RF magnetron sputtering,we fabricated a MSM type Ga₂O₃ solar-blind UV detector with high performance:Firstly,the effect of growth pressure on the quality of epitaxial gallium oxide film on rigid sapphire substrate and the corresponding performance of solar-blind UV detector were studied.The tests showed that the quality of gallium oxide film was the best when the growth pressure was 25 m Torr.At the same time,the detection performance of the device corresponding to the Ga₂O₃ film deposited at the growth pressure of 25 m Torr was also the best.Then,we studied gallium oxide solar-blind UV detectors based on flexible substrate.After bending fatigue tests of 500times at the bending degree r=4 mm,the photodetectors still showed stable test results,proving that the flexible gallium oxide solar-blind UV detector had good robustness and satisfactory flexibility.Finally,we studied the visible-transparent Ga₂O₃ solar-blind UV detector based on ITO electrode.Compared with the traditional Ga₂O₃ solar-blind opaque UV detector based on Ti/Au electrode,ITO based visible-transparent Ga₂O₃ solar-blind UV detector had better detection performance.2.High performance schottky barrier photodiode type solar-blind UV detector was prepared based onβ-Ga₂O₃ nanomembrane（NW）obtained by stripping fromβ-Ga₂O₃ single crystal and transferring process:The specific detectivity D^*was 2×10¹⁶ Jones.This index was the highest among the Ga₂O₃ schottky barrier photodiode type solar-blind UV detectors reported at that time.Then,through simulation,it was found that the electric field is concentrated near the anode metal.The peak electric field reached 5.3 MV/cm,thus inducing the collision ionization effect,which is the key point to achieve a high performance detector.3.Based onβ-Ga₂O₃ NW,a high performance phototransistor type solar-blind UV detector with top gate structure was fabricated:Firstly,the Hf O₂ gate dielectric with high dielectric constant and ultra-thin Ni/Au（2/10 nm）gate metal were introduced to improve the performance of the solar-blind UV phototransistor（SBPT）.Due to ultra-strong control ability of gate and high solar-blind UV transmittance of gate metal,theβ-Ga₂O₃ SBPT based on the structure of top-gate had high detection performance.The specific detectivity D^*was1.1×10¹⁹ Jones,which was the highest index reported among all types of Ga₂O₃-based photodetectors of the same period.Then,in order to optimize the surface quality ofβ-Ga₂O₃active layer and the interface quality ofβ-Ga₂O₃/dielectric layer,we introduced low temperature in situ ozone treatment technology to pretreat the surface of gallium oxide materials.Through comparison,it was found that the content of metastable Ga-O bond onβ-Ga₂O₃ surface could be significantly reduced after low temperature in situ ozone treatment.In addition,compared with the devices without low temperature in situ ozone treatment,the photoelectronic characteristic parameters of the treated devices all had different degrees of improvement,these obviously optimized parameters illustrated that ozone pretreatment is indeed an effective method to improve the performance ofβ-Ga₂O₃ based SBPT.Finally,in order to achieve a more simplified peripheral matching circuit and a smaller device power consumption,we fabricated and studied the phototransistor typeβ-Ga₂O₃ solar-blind UV detector working at zero gate bias.The device showed extremely high detection performance.4.A solar-blind UV communication system was built to realize real-time solar-blind UV communication:Based on high-performance gallium oxide thin film based MSM solar-blind UV detector,we developed a solar-blind UV communication system independently,which realized the real-time UV optical communication function of gallium oxide solar-blind for the first time.At the same time,the system could be tested under fluorescent lamp without interference.