| Schottky barrier diodes are unipolar rectifiers based on metal-semiconductor contacts,which have a lower turn-on voltage.Because the charge storage effect of the minor carrier in the Schottky diode is very small,and its reverse recovery time is short,it can be used to prepare high-frequency or fast switching devices.The preparation process of a Schottky detector is basically similar to that of a Schottky diode.Compared with general detectors,it has the advantages of low cost,simple process,and so on,so it has great commercial prospects.As a recently popular semiconductor material,gallium oxide(Ga2O3)has many good characteristics such as ultra-wide band gap,high breakdown electric field,and stable chemical properties.It is very suitable for manufacturing Schottky diodes and Schottky detectors.Therefore,research on Ga2O3 Schottky devices has always been a popular direction.This article focuses on gallium oxide Schottky diodes,and studies three aspects,as follows:First,we prepared a PEDOT:PSS film on a high-quality gallium oxide substrate by mechanical stripping and spin coating,and made ohmic contacts on the back of the substrate to develop a PEDOT:PSS/Ga2O3 Schottky diode with a vertical structure.Through multiple electrical tests on the device,we obtained the reverse leakage current(less than 10-9A@-3 V),the current switching ratio(107),and the Schottky barrier height(1.46 e V)of the device.All these show that the PEDOT:PSS/Ga2O3 Schottky diode has good rectification performance.Then,we conducted an in-depth analysis of the device's transmitter.Through the temperature-varying I-V test(300-425 k),it was found that the barrier height ?b and the ideal factor n change with temperature.By extracting the effective Richardson constant of the device,we determined that the cause of this phenomenon is the non-uniformity of the Schottky barrier,and finally through the Thermionic Emission theory(TE)with Gaussian distribution,we obtained the average Schottky barrier height((?))and the standard deviation(?s)of the barrier(1.57 e V,0.212 e V),and the effective Richardson constant(10.8 Acm-2k-2)of the device.Finally,in order to improve the performance of PEDOT:PSS/Ga2O3 Schottky diodes,we have improved the process(adding a metal transport layer on the surface of PEDOT:PSS,using a high doping concentration Ga2O3 substrate).Through the analysis of the experimental results,we found that the performance of the device was greatly improved by adding a metal transport layer,but the device was not much improved by using a highly doped substrate.Second,we studied the characteristics of the detector on the prepared PEDOT:PSS/Ga2O3Schottky diode,and performed a complete test of the device(light and dark current,response time and spectral responsivity).From the test results,we obtained the detector's dark current(9.4 n A@-4 V)and light-dark current ratio(48),indicating that the device has low noise characteristics.And the device also has photoelectric effect(short circuit current Isc=1.68 n A,open circuit voltage Voc=0.15 V).In the test,we also observed the non-linear increase of the photocurrent of the device with the optical power density,and finally explained this phenomenon by analyzing the effect of the surface state on the Schottky barrier band structure.The time response curve of the detector is stable and repeatable with the change of illumination,and the rise time and decay time are 396 ms and 289 ms,respectively.The faster response speed also indicates that the substrate material has fewer defects.The peak value of the responsivity R of the detector is 0.62 A/W,and the ratio of the responsivity of different light wavelengths(R254nm/R400nm)is 1.26×103,which illustrates the good spectral selectivity of the device.And calculated from the responsivity R that the device has a high external quantum efficiency(EQE)(315%).Third,we prepared Au/Ni/(InGa)2O3 Schottky diodes using epitaxial films as substrates and studied their electrical characteristics.Using similar testing and analysis methods as in Part I,we investigated its electrical characteristics and carrier transport mechanism.The device has a high forward saturation current density(65 A/cm2),a low on-resistance of23.48 m?·cm2,and a high current switching ratio(108),which reflects the good rectification characteristics of a diode.At the same time,it was observed that the device also had the phenomenon(the Schottky barrier height?b and the ideal factor n change with temperature)that appeared in the first part.In the end,we used the same analysis method,that is,the Thermionic Emission theory(TE)added with the barrier Gaussian distribution explains this phenomenon,and calculated that the average barrier height of the device is1.18 e V,the standard deviation of the barrier is 0.135 V,and the(In Ga)2O3 effective Richardson constant A*is 42.34 Acm-2k-2. |
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