The Fabrication And Performance Optimization Of Sandwich Structure ZnO-Based Ultraviolet Photodetectors

ZnO is a semiconductor material with a wide direct band gap and the MgZnO alloy can be prepared by doping Mg element,the band gap is adjustable from 3.3 to 7.8 eV.Aiming at resolving the existed problem which the low absorption of ZnO-based MSM UV photodetecctors?PDs?.In this paper,by controlling the growing parameters,ZnO-based thin films have been achieved,and designed the ZnO/Au/ZnO sandwich structure ultraviolet PDs.Then introduce MgZn O material,and the Mg_0.2Zn_0.8O/Au/ZnO and Mg_0.5Zn_0.5O/Au/ZnO sandwich structure PDs have been designed.The PDs of visible band and solar-blind are realized.The performance of sandwich structure PDs is systematically characterized.The main researches are as follows:?1?In order to increase the absorption of the PDs,a sandwich ZnO/Au/ZnO?300 nm?ultraviolet PDs was designed.Then by regulating the thickness of the Au electrode,it was found that the PDs performance was optimize when the Au electrode thickness was 20 nm,and the response of ZnO/Au/ZnO?300 nm?PDs was 9.76 A/W under 5 V bias.On the basis of this,the heat annealing treatment of the ZnO?S₁?film is carried out,when the annealing temperature at 700?,and the response of ZnO?S₁?/Au/ZnO?300 nm?PDs was 69.96 A/W nearly 7.17 times after the treatment of annealing.?2?In order to broaden the blind detector in the visible band wavelength,introduction Mg_0.2Zn_0.8O materials.Firstly,by changing the positions of Mg_0.2Zn_0.8O and ZnO double-layer film,it was determined that the performance of Mg_0.2Zn_0.8O/Au/ZnO?300 nm?sandwich structure PDs was better.Then put Mg_0.2Zn_0.8O film thickness as the experimental variables,to optimize the performance of sandwich structures.When the film thickness of Mg_0.2Zn_0.8O is 300 nm,the peak response was higher reaches 117.42 A/W under 35 V bias.This is because with the thickness of the film,the width of the depleted layer is affected,so the electrical performance of the PDs is affected?3?The avalanche sandwich ZnO-based ultraviolet PDs was successfully prepared.High quality Mg_0.5Zn_0.5O films were grown by magnetron sputtering can detect the solar blind band,and then the thickness of ZnO films was changed to regulate the electric field intensity.At 18 V bias,the response of Mg_0.5Zn_0.5O/Au/ZnO?100 nm?PDs exceeded 2.5×10³ A/W,which increased by 38 times compared with 17 V bias.Based on the analysis of the I-V curve,it is concluded that the avalanche multiplier effect leads to the high gain of the PDs.However,in ZnO/Au/ZnO?300 nm?and Mg_0.2Zn_0.8O/Au/ZnO?300 nm?structural PDs,avalanche doubling phenomenon did not occur,because the ZnO film grows on the top of the PDs and is in close contact with the finger electrode,the thickness of the ZnO film will directly affect the transmission of the forked finger electrode to the electrical signal.