Preparation And Simulation Research Of Photodetector Based On GaN HEMT Photosensitive Gate

With the widespread application of ultraviolet light,high-performance UV photodetector(UV PD)has become more and more important.Improving the spectral responsivity and transient response characteristics of UV PD is the main direction of research on detectors.The current UV detection wavelength band is concentrated in200?400nm,and the materials are mainly third-generation broadband semiconductors.In particular,in electronic devices based on GaN materials,there are GaN HEMTs that use two-dimensional electron gas(2DEG)at the GaN/AlGaN heterojunction interface to work.Its 2DEG concentration is easily controlled by the AlGaN surface state and the gate voltage,which can realize the significant change of the source-drain output characteristics of the HEMT.This feature provides a new idea for the development of high-sensitivity,high-response UV PD.This paper uses ferroelectric materials with abnormal photovoltaic effect and ferroelectricity and ZnO nanowires(Nanowire,NW)whose conductivity can be changed by ultraviolet light as the photosensitive-gate,combined with the characteristics of GaN HEMT grid control.Use the photosensitive-gate to control the gate voltage and surface state of the GaN HEMT with or without light.The GaN HEMT UV PD with high response to ultraviolet light has been studied.In order to improve the HEMT gate control capability,the transconductance of different trench gate GaN HEMTs simulated by Silvaco increases with the increase of the trench gate depth.The experiment uses ICP etching to obtain HEMT with 10/15nm groove gate.The threshold voltage of the device has increased from-5.2V for a grooved gate to-1.3V for a 15nm grooved gate.The voltage corresponding to peak transconductance shifts from-1.8V to 0.6V.The peak transconductance of the device increases to 70mm/m A in the 15nm groove.At the same time,by longitudinally etching below the source and drain electrodes(S/D)of the device,stacked Ti/Al/Ti/Al/Ti/Al/Ni/Au and non-stacked Ti/Al/Ni/Au are used as S/D.After annealing at 850°C for 35s under N₂ environment,it is found that the laminated S/D resistivity is lower,and vertical etching under S/D can further improve the ohmic characteristics of the device.In the research of ferro-inductance photosensitive-gate.The PZT ferroelectric thin film obtained by sputtering under Ar:O₂=1:1 atmosphere is annealed at 650°C for 1 min,and the PZT with a ZnO bottom electrode buffer layer is obtained without pyrochlore phase;the surface of the film is flat,and the crystal grains are larger and uniform;The PZT columnar crystal growth orientation is obvious,and the crystal grains are closely arranged.In addition,the polarization performance of the ZnO/PZT film is basically unchanged after 6×10~6 switching cycles of 1KHz frequency under 30V bias voltage,and the ferroelectric fatigue resistance is better.However,after the ferroelectric thin film is integrated on the GaN HEMT gate,it needs to be annealed to form a good crystalline state.This process easily causes the HEMT electrode to agglomerate and oxidize at high temperature,which affects the detection performance of the device.Finally,integrate ZnO/PZT on a GaN HEMT gate with a gate length of 3?m,a gate-source and gate-drain spacing of 6?m and 8?m.Obtained under 365nm ultraviolet light with an optical power density of320 m W cm~2,a source-drain current difference of 11.0m A,a responsivity of 106.1A W,and a response time of ?_r?0.12s and?_f?8.2s of the ferro-inductance photosensitive-gate GaN HEMT UV PD in the light and dark field.Subsequently,ZnO NW,which is easier to integrate in the HEMT gate,was used instead of the ferro-inductive photosensitive-gate.With or without light,NW can achieve the regulation characteristics of NW conductivity and AlGaN interface barrier through the adsorption and desorption of oxygen molecules.Thus,ZnO NW is used instead of ferro-inductance photosensitive-gate to realize HEMT UV detection.When growing ZnO NW by hydrothermal method,it is found that under the same growth time,the diameter of NW is larger and the length is longer when the seed layer is 200nm thick;however,the vertical growth orientation of NW gradually disappears with the increase of growth time.The ZnO NW obtained on the 100nm thick seed layer has better vertical growth orientation.Compared with the Si substrate,the ZnO NW obtained on the GaN substrate has better crystallinity.By analyzing the optical characteristics of the GaN HEMT integrated with ZnO NW,NW effectively increases the light absorption of the device in the ultraviolet band.Therefore,using ZnO NW as a GaN HEMT photosensitive-gate,a high-performance metal electrode NW photosensitive-gate GaN HEMT UV PD with 1.15×10~4A W responsivity and a response time of?_r=10ms and?_f=250ms at a wavelength of 265 nm is obtained.