Study On Gallium Doped ZnO Films And Devices Prepared By Pulsed Laser Deposition

With the increasing awareness of environmental protection,display materials and devices are required to be lower cost and more environmentally friendly.Gallium doped zinc oxide?GZO?material is free of In and is green and non-toxic.In addition,the GZO film can be used both as an active layer of a thin film transistor?TFT?and as an electrode layer of a TFT,which is beneficial to simplifying the device manufacturing process and reducing costs.In this paper,the GZO films were studied systematically,and the optimized GZO films were used to prepare the active layer and the source drain electrodes of TFT,which can provide a reference for the research of green TFT devices.First of all,the preparation of GZO thin films by pulsed laser deposition is systematically studied.The effects of laser energy,laser frequency,film thickness,deposition oxygen pressure,annealing temperature,and Ga doping content on the structure,morphology,and photoelectric properties of GZO films were investigated.The results show that:?1?when the laser energy and laser frequency are 450m J and 5Hz,the GZO film has the best photoelectric performance and the lowest density of defects;?2?When the thickness of the GZO film is 65nm,the film resistivity is lower than 3×10^-5?·m and the light transmittance can reach 81.57%.The ultra-thin GZO film has small surface roughness,few surface defects,and is amorphous,which is expected to be used in the active layer of TFT;?3?The increase in oxygen pressure will cause the conductivity of the film to drop sharply,because oxygen can enter the film to fill the oxygen vacancies;?4?The film prepared by using a GZO target with a Ga₂O₃ content of 2wt%has the best photoelectric performance;?5?The prepared GZO film has a lower phase transition temperature?300??,because the particle beam emitted by the pulse laser has the characteristics of high temperature and high density,indicating that the PLD method helps to reduce the annealing temperature.Secondly,the TFT device with a GZO active layer was studied,and the effects of the thickness of the GZO layer and the deposition oxygen pressure on the performance of the TFT were investigated.The results show that too thin active layer carrier concentration is too low,too thick active layer has high roughness and the device has a large off-state current,and the optimal film thickness is about 27nm;TFTs prepared without oxygen will exhibit high conductance.When the oxygen concentration is too high,receptor-defective complexes such as Ga _Zn-O_inand Ga _Zn-V_Zn are easily formed.The optimal deposition oxygen pressure is 1.0 Pa.The GZO-TFT device exhibits a?_satof 12.32 cm²/V·s,an I_on/I_off of 9.17×10⁶,a V_thof 4.93V and an SS of 1.53 V/dec.Finally,the TFT device with GZO source and drain electrodes was studied,and the effects of Ga doping content and annealing temperature on TFT performance were explored.The results show that the device exhibits the best electrical performance and bias stability when the source and drain electrodes are prepared at room temperature using a GZO target doped with2wt%Ga₂O₃.The negative bias stress of the TFT device has basically no drift and the positive bias stress drift is as low as 2V.The device exhibits a?_satof 12.22 cm²/V·s,an I_on/I_off of 6.4×10⁷,a V_thof 1.96V and an SS of 0.082V/dec.The contact between the source-drain electrode and the active layer of the device is an ohmic contact and the contact resistance is very low.Theminimum R_SD and R_SD-eff are 2.0K? and 9.15×10^-3?·cm²?...