Preparation and Properties of PEN Substrate Gallium Oxide Based Flexible Ultraviolet Detector(Invited)
The emerging wide-band gap semiconductor material gallium oxide is a very promising solar blind ultraviolet detector material,which has the advantages of good stability,simple preparation process,low production cost,high temperature and high pressure resistance,etc.And the preparation materials used as flexible photodetectors can maintain good performance even when they are twisted and extended into complex non-planar shapes.However,due to the limitation of substrate temperature(generally less than 200℃),it is difficult to directly grow high-quality gallium oxide films on flexible substrates,which seriously affects the improvement and promotion of the performance of flexible ultraviolet detectors.At present,most of the transparent conductive thin flexible substrates Ga2O3 reported were prepared by magnetron sputtering method,so in order to improve reliability,we also adopted magnetron sputtering method in this experiment.The experimental process of preparing the flexible gallium oxide Ultraviolet(UV)detector on the PEN substrate is planned as follows:First,a Ga2O3 adhesive layer is formed by pre-sputtering with DE500 magnetron sputtering equipment,and on this basis,a Ga2O3 thin film with a thickness of about 160 nm is further deposited.Finally,ITO electrode layer with thickness of about 150 nm was grown on the thin film by magnetron sputtering through the mask.The process parameters of growing Ga2O3 film on PEN substrate and ITO electrode on Ga2O3 film were set.It can be seen from the results of the structure characterization of the thin films that the XRD patterns of the PEN substrate and the PEN substrate growing gallium oxide thin films are compared,and there is only a strong diffraction peak at 25.9° in the curve,but no other diffraction peaks.This indicates that the prepared GAN films have amorphous or microcrystalline structure.The full spectrum scanning of 0～1 200 eV and fine scanning of Ga 2p and O 1s were obtained.The atomic ratio of Ga and O in the prepared film is about 0.67,which is very close to the theoretical stoichiometric ratio of gallium oxide,indicating that the chemical composition of the film is accurate.The optimal spectral response of the gallium oxide photodetector from 200～400 nm corresponds to the excitation at 214 nm.The analysis shows that the average transmittance of the sample in the visible region exceeds 80%.The sample transmittance of Ga2O3 films grown in some wavelength region is higher than that of PEN substrate,which is caused by the anti-reflection effect of refractive index modulation.By observing the surface morphology of the film,it can be seen that the Ga2O3 UV detector film and ITO electrode on the PEN substrate only show slight bending traces in the bending region,and the ITO electrode of the whole sample does not appear to be broken.Therefore,it is proved that the prepared PEN substrate gallium oxide UV detector has good flexibility and bending resistance.By comparing the light and dark current curves of the device graph before and after 20 000 bending,it can be observed that the light and dark current ratio of the UV detector after 20 000 bending does not decrease significantly.According to the I-t characteristic curve of the response of the flexible Ga2O3 UV detector to 254 nm UV switch at 10 V bias voltage after 20 000 bending,it can be seen that after the alternating opening and closing of the UV light source for 10 cycles,the current response of the detector shows a continuous rapid rise and fall,and the I-t characteristic curve presents periodic stability.It is proved that the Ga2O3 UV detector prepared on PEN substrate has excellent photoelectric performance and mechanical resistance,which provides an experimental basis and theoretical support for the development of high-performance flexible UV photodetectors.
Semiconductor photodetectorFlexible ultraviolet detectorRadio frequency magnetron sputteringGallium oxidePolyethylene glycol naphthalene dicarboxylateIndium tin oxide
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