基于感光栅极GaN高迁移率晶体管的新型探测器制备与优化

利用GaN高电子迁移率晶体管(HEMT)的栅控特性和锆钛酸铅(PZT)铁电薄膜的光伏效应,在HEMT器件的栅极处沉积一层PZT铁电薄膜,提出了一种新型的(光敏感层/HEMT)探测结构.为制备出光伏性能优异的薄膜,对不同的溅射功率和退火温度制备的PZT铁电薄膜进行表面形貌和铁电性能分析.发现200 W溅射功率、700℃的退火温度制备的薄膜表面晶粒生长明显,剩余极化强度为38.0μC·cm-2.工艺制备GaN基HEMT器件并把PZT薄膜沉积到器件栅极上.在无光和365nm紫外光照射下对有、无铁电薄膜的HEMT探测器的输出特性进行测试.结果显示,在光照时,有铁电薄膜的HEMT器件相较于无光时,源-漏饱和电压最多降低3.55V,饱和电流最多增加5.84mA,表明新型感光栅极HEMT探测器对紫外光具有优异的探测效果.为实现对新型探测器的结构进行优化的目的,对栅长为1μm、2μm和3μm等不同栅长的探测器进行光照测试.结果表明,在紫外光照射下,三种探测器的漏极饱和电流分别为23mA、20mA和17mA,所以栅长越长器件的饱和电流越小,探测性能越差.

Preparation and Optimization of Photosensitive Gate GaN-based High Electron Mobility Transistor Devices

Based on the gate controlled characteristics of GaN High Electron Mobility Transistors(HEMTs)and on the photovoltaic effect in lead zirconate-titanate(PZT)ferroelectric thin films,a new type of photosensitive layer/HEMT detector structure is proposed.For this purpose,a PZT ferroelectric thin film is deposited on the gate of a HEMT device to prepare films with optimized photovoltaic performance,the surface morphology and ferroelectric properties of PZT films prepared by different sputtering powers and annealing temperatures are analyzed.It is found that the best conditions for the grain growth on the surface of the film are at 200 W sputtering power and 700℃annealing temperature,and the residual polarization intensity is 38.0μC·cm^-2.The output characteristics of the fabricated photosensitive gate PZT/GaN-based HEMT devices are compared to those of pristine HEMTs under both dark condition and 365 nm ultraviolet light.The results show that the source drain saturation voltage of the HEMT with the ferroelectric thin film decreases by 3.55 V and the saturation current increases by 5.84 mA,compared with those without light,clearly indicating a significant UV photodetection capability.To achieve the purpose of optimizing the structure of the new type of detector,detectors with different grid lengths such as 1μm,2μm,and 3μm are tested.The results show that under ultraviolet light,the drain saturation currents of the three detectors are 23 mA,20 mA,and 17 mA,respectively.Therefore,the longer the gate length,the smaller the saturation current of the device,and the worse the detection performance.