退火温度对氧化镓薄膜及紫外探测器性能的影响

Effects of annealing temperature on properties of gallium oxide thin films and ultraviolet detectors

采用射频磁控溅射法在石英基底上制备Ga_(2)O_(3)薄膜,并在氩气气氛中控制不同的退火温度进行后退火,通过对样品的晶体结构、透射率、表面形貌和光学带隙等性质进行测试分析,发现退火工艺可以提升薄膜的结晶质量,但同时高温退火也容易使得薄膜中的氧元素逸出薄膜外形成氧空位,选取800℃退火后样品制备成金属-半导体-金属(metal-semiconductor-metal,MSM)型光电探测器件,并与未退火样品器件对比发现在1.1 V的反向偏压下,800℃的光暗电流比为1021.3、响应度为0.106 A/W、比探测率为1.61×10^(12)Jones,分别是未退火器件的7.5,195和38.3倍,外量子效率相较于未退火样品提升了51.6%,上升时间(0.19/0.48 s)相较于未退火样品(0.93/0.93 s)减小,下降时间(0.64/0.72 s)与未退火样品(0.45/0.49 s)相比有所增大,表明氧空位的增加可以减缓光生载流子的复合来达到延长载流子寿命的效果,最后详细分析了退火后氧空位的增多导致探测器性能参数提高的机理.

In this work,gallium oxide(Ga_(2)O_(3))thin films are deposited on quartz substrates by radio frequency magnetron sputtering at room temperature and annealed in argon atmosphere at different temperatures.The influences of annealing temperatures in the argon atmosphere on crystal structure,transmittance,surface morphology,and optical band gap of the samples are investigated in detail.It is found that the annealing process can improve the crystalline quality of the film,but high-temperature annealing can also easily cause oxygen elements in the film to escape from the film to form oxygen vacancies,which is evidenced by XPS test results.To obtain the effect of the annealing process on the performance of gallium oxide thin film detector,the metal-semiconductor-metal(MSM)photodetector based on the sample annealed at 800℃,which is compared with untreated sample operated at a reverse bias voltage of 1.1 V,can achieve excellent comprehensive photo-detection properties for 254 nm ultraviolet light:the light-dark current ratio(I254/Idark),responsivity and specific detectivity are as high as 1021.3,0.106 A/W and 1.61×10^(12)Jones,respectively,which are 7.5,195 and 38.3 times those of the unannealed sample device.And the external quantum efficiency is improved by 51.6%.The rise time of sample detector(0.19/0.48 s)annealed at 800℃decreases compared with that of the unannealed sample(0.93/0.93 s),and the descent time of 800℃detector(0.64/0.72 s)increases compared with that of the unannealed sample(0.45/0.49 s),respectively.By comparing the parameters with those of other current gallium oxide-based MSM photodetectors,it is found that the detector parameters of this work have some gaps compared with the current optimal parameters,which is attributed to the fact that the quartz substrate is selected for this work and not the sapphire substrate that is better matching with gallium oxide,resulting in the poor quality of the film compared with that of the sample on the sapphire substrate,and in this work,the photodetector has the high light-dark current ratio(PDCR)and detection rate(D^(*)).In the end,the mechanism of increasing oxygen vacancies after being annealed,which leads to the improvement of detector performance parameters,is analyzed in detail.