Developement Of Flexible Ga₂O₃ Schottky Barrier Diode

In recent years,flexible devices have gradually emerged in the field of electronic technology.Applications such as folding electronic devices,wearable energy harvesting systems,soft portable devices and photodetectors are booming.As a third-generation new semiconductor material,Ga₂O₃ has the characteristics of ultra-wide bandgap wand high theoretical breakdown field,which is very suitable for making power devices.However,most of the studies related to Ga₂O₃ Schottky diode(SBD)are only performed on rigid substrates.In this paper,the research work of flexible Ga₂O₃ Schottky diodes is carried out from the following aspects:First,muscovite,which can withstand at least 600?high temperature,is selected as the flexible substrate material.?-Ga₂O₃ flake is mechanically exfoliated and transferred to Muscovite substrate by scotch tape method,and then the flexible lateral?-Ga₂O₃ Schottky diode is fabricated.The thickness of?-Ga₂O₃ flake is 380nm,and its current density voltage(J-V)characteristics are basically the same as those of diodes on rigid substrates.The results show that the flexible lateral?-Ga₂O₃ SBD still has decent current on/off ratio:around 10⁶?10⁷,the on-resistance is as low as 85 m?·mm,the turn-on voltage(V_on)is about 0.6 V,and the reverse breakdown voltage is 485 V.Bending test and fatigue test were performed on the device.The forward J-V curve of the flexible diode at the bending length d of 14mm,12mm,10mm,8mm,and 6mm is basically the same as that in the flat state.The forward and reverse J-V characteristics of the flexible device were tested at 0 cycle,100 cycles,300 cycles,and500cycles.It is found that after the device is repeatedly bent 500 cycles,the forward current decreases,the reverse leakage increases,the breakdown voltage drops from 485V to 290V,and the performance is slightly degraded.It shows that the flexible?-Ga₂O₃ Schottky diodes fabricated by us not only have the same excellent device performance as those on the rigid substrate,but also have certain stretch and ductility.Second,in order to overcome the problem that most of the flexible substrate materials are not resistant to high temperature,we found a method to achieve good ohmic contact at room temperature:insert ultra-thin insulating material hexagonal boron nitride(h-BN)between ohmic metal and?-Ga₂O₃ semiconductor material to form metal insulator semiconductor(MIS)structure.Then?-Ga₂O₃ SBD was prepared by this method.The transmission line model(TLM)is used to measure the resistance between metal and?-Ga₂O₃ in MIS structure.The specific contact resistivity is 8.3×10^-4?·cm^-2,and the sheet resistance R_sh of semiconductor thin film material is 1.2×10⁴?/?.The current density voltage characteristics of the diode at room temperature show that the device has excellent rectifying characteristics.The on/off ratio(I_on/I_off)of the device is about 10⁶,the on-resistance is 133m?·mm,the turn-on voltage V_on is 0.78V,and the breakdown voltage 1300V,which indicates that it has the potential of excellent power devices.The forward J-V characteristics at different temperatures show that the turn-on voltage V_on decreases from 0.74V to 0.56V with the increase of temperature(from 25?to 175?).However,the current and voltage characteristics of the device at all temperatures have a similar trend,indicating that the device can still maintain excellent electrical characteristics at 175?.With the increase of temperature,the ideal factor decreases from 1.62 to 1.18,which indicates that there is a current mechanism other than thermal emission due to the inhomogeneity of Schottky barrier contact.Third,in order to further increase the breakdown voltage of the device,we designed a new terminal Moat structure for?-Ga₂O₃ SBD using simulation software.The device has been simulated with different etching angles(30°,45°,60°,75°,90°),and it is found that the maximum breakdown voltage is 970 V when the etching angle is 90°.Due to the strong electronegativity of fluorine ion,the electric field concentration effect can be alleviated.Further fluorine ion implantation is carried out on the basis of Moat structure.The depth of fluorine ion implantation is 0.2?m,and the implantation concentration is 10¹³cm^-3.The simulation of different etching angles shows that the breakdown voltage of the device can reach 2250 V at 45°etching angle.The simulation also provides a valuable reference for the subsequent actual process tape-out.A high-performance SBD with a breakdown voltage of2250 V is demonstrated using the optimized edge termination based on Moat etch and fluorine ion implantation.