Research On Low Power AlGaN/GaN Schottky Barrier Diode

Mobile electronic products,smart home appliance products,photovoltaic power stations,data centers,electric vehicles and other high efficiency,high power and compact power supply have put forward more and more urgent needs.The third-generation semiconductor power electronic devices represented by gallium nitride(GaN)and silicon carbide(Si C)have attracted much attention from the industry and academia in recent years due to their advantages of high speed,high efficiency and high power.Because GaN material has high breakdown field strength,high electron drift speed and can form two-dimensional electron gas with high density and high mobility,it has become an important new technology for manufacturing high voltage(high power)resistance and low conduction resistance(high efficiency),which has attracted the attention of researchers and enterprises in recent years.Currently,GaN power electronics devices that attract the most attention are GaN HEMT power switching devices and GaN schottky diodes.Thesis mainly around the current mainstream of GaN base diode structure namely AlGaN/GaN schottky diode to carry out the research,the main research goal is to continuously optimize the device structure and process,reduce the device open when he worked in positive bias voltage,conduction resistance and leakage current reverse bias is working pressure and high pressure environment ability,reduce the power dissipation of the device.To this end,this paper focuses on the study of AlGaN/GaN SBD devices with recessed anode structure,and reduces the dissipated power of the devices by optimizing the etching depth of the recessed anode and the anode metal material.The main research results of this paper are as follows:(1)the effect of etching depth of different grooves on device performance was simulated.The simulation results showed that the device opening voltage decreased gradually with the etching depth increasing,and the conduction current increased with the etching depth increasing.Ni anode metal anode structure was completely etching grooves and conventional etching device structure,the results showed fully etching grooves anode structure components compared with conventional etching device not open voltage from 1.77 V to 0.74 V,3 V current flow increases 4.27 times,while the reverse leakage current to reduce a majority of orders of magnitude,consistent with the simulation rule change trend.The analysis shows that because the anode metal is in direct contact with the two-dimensional electron channel layer,the short-base junction presents a very narrow triangular barrier.Compared with the wider ladder barrier at the short-base junction of the conventional device,the 2DEG tunneling current can be formed more easily,and the effect of reducing the device's starting voltage can be achieved.(2)silvaco simulation was performed on three different metal anode devices.The results showed that the switching voltage Cr < W < Ni,the current density Cr > W > Ni and the reverse leakage Cr > W > Ni at the same voltage.Three different metal anodes were prepared under the same technological conditions.The results showed that the starting voltage of Cr anode device was 0.17 v,the conduction current of the device was 276.92 m A/mm,the differential conduction resistance was 6.83 m A/mm,and the reverse leakage was 7.08 m A/mm at 3V.When the starting voltage of W anode device is 0.47 v,the conduction current of the device is 276.42 ma /mm,the differential conduction resistance is 6.39,and the reverse leakage is 3.48×10-4 m A/mm.The opening voltage of the Ni anode device is 0.98 v,and the conduction current of the device is 262.32 ma /mm at 3V,the differential conduction resistance is 7.49,and the reverse leakage is 6.07×10-6 m A/mm.The results are consistent with the simulation law.According to the experimental results,compared with the conventional anode metal Ni of devices,metal W can reduce the device's starting voltage,but will increase the reverse leakage by nearly two orders of magnitude.Metal Cr can obtain the lowest starting voltage,but the rectifier characteristic is poor.Reverse leakage is extremely great.(3)to study the three kinds of metal forming schottky contact with GaN material respectively,XPS test design and preparation of samples,the results showed that Cr contact with GaN material formation of the schottky barrier height of the lowest 0.29 e V,W,Ni,and GaN material formation of the schottky barrier height 0.69 e V and 0.96 e V,respectively,with logarithmic coordinates i-v curve fitting for the barrier height of close,verify the anode groove side work of the main current channel to the device.(4)finally,we analyze the reverse leakage mechanism of W anode device.The main leakage mechanism of the device is the thermal electron emission model under the bias voltage from 0 to-1v.Under the bias voltage from-1 to-5v,the device leakage is led by frenkel-poole emission mechanism,and the trap energy level position is extracted 0.262 e V.At the bias voltage above-5v,device leakage is mainly dominated by the trap-assisted tunneling model.