| Gallium nitride(GaN),as a representative of the third generation of semiconductor materials,has a series of excellent electrical characteristics such as high band gap,high electron mobility,high electron saturation speed,and high breakdown field strength.It has been widely used in the fields of power electronics and microwave radio frequency.This article studies the Gallium Nitride Schottky Diode(GaN SBD)based on the high-voltage and high-power field.Aiming at the current high turn-on voltage and low breakdown voltage of GaN SBD,this paper studies and prepares a new hybrid anode structure Schottky diode(HA-SBD),in order to obtain a low turn-on voltage while obtaining a high reverse breakdown voltage.The main research contents and results of this paper are as follows:1.Through Atlas-Silvaco simulation software,perform simulation research on the following four structures:the traditional Schottky diode(C-SBD),the partial recessed Schottky diode(PR-SBD),the fully recessed Schottky diode(FR-SBD)and the hybrid anode Schottky diode(HA-SBD).The simulation results show that HA-SBD has the most excellent forward characteristics.The current density at 3V is almost the same as FR-SBD,but the turn-on voltage is extremely low,only 0.26V.The reverse breakdown voltage of HA-SBD is slightly lower than that of C-SBD,which is similar to the other two types of diodes.In terms of overall performance,the performance of HA-SBD is even better.In addition,a simulation study was conducted on the groove length of HA-SBD,and it can be found that when the groove length is 4?m,the device has good forward and reverse characteristics.2.The etching quality of the groove seriously affects the performance of the device.This paper optimizes and develops an etching formula with low etching rate and low surface damage:the power of the upper electrode is 150W,the power of the lower electrode is 5W,the gas type and the flow rate is BCl3/Cl2=20sccm/8sccm,the pressure in the reaction chamber is 5m T,and the temperature in the reaction chamber is 25?.A groove etching formula with controllable etching rate and minimal surface etching damage is obtained.The etching rate is only 3.03nm/min.In the actual fabrication of the device,HA-SBD can be divided into two categories according to the depth of groove etching,one is the fully recessed hybrid anode Schottky diode(FRHA-SBD),and the other is the partial recessed hybrid anode Schottky diode(PRHA-SBD).3.The electrical characteristics of FRHA-SBD and PRHA-SBD with different cathode and anode distances are tested.The results show that as the cathode and anode distances increase from 6?m to 34?m,the turn-on voltage of FRHA-SBD stabilizes at about 0.68V,and the characteristic on-resistance changes from 0.625 m?·cm2 rose to 6.624 m?·cm2,breakdown voltage rose from 159V to 886V,Baliga figure of merit(BFOM)rose from 40.43 WM/cm2to 118.19 WM/cm2.The turn-on voltage of PRHA-SBD is stable at about 0.35V,the characteristic on-resistance rises from 0.702m?·cm2 to 8.2m?·cm2,and the BFOM value rises from 33.78WM/cm2 to 97.032WM/cm2.This shows that the increase in the distance between anode and cathode can significantly improve the power performance of the device within a certain range.4.The electrical characteristics of FRHA-SBD and PRHA-SBD with different field plate lengths are tested.The results show that as the field plate length increases from 1?m to 4?m,the forward performance of the device hardly changes,and the turn-on voltage of FRHA-SBD is around 0.68V,the differential on-resistance value is(6.82±0.08)?·mm,and the reverse breakdown voltage of the device rises from 300V to 385V.The turn-on voltage of PRHA-SBD is around 0.35V,the differential on-resistance value is(6.95±0.12)?·mm,and the reverse breakdown voltage of the device rises from 295V to 377V.This shows that the introduction of the field plate can modulate the electric field distribution at the edge of the schottky contact and improve the breakdown performance of the device.However,the introduction of the field plate brings parasitic capacitance,which reduces the characteristic frequency of FRHA-SBD from 6.56GHz to 4.81GHz,and the characteristic frequency of PRHA-SBD from 1.175GHz to 1.107GHz.5.In view of the large reverse leakage of PRHA-SBD and low current switching ratio,this paper adopts the post anode metal deposition annealing(PAA)process.The experimental results show that when the annealing temperature is 450?,the reverse leakage of the device is reduced to the order of 10-3mA/mm,the current switching ratio increased from 103 to 106,which shows that the PAA process can repair the etching damage in the groove area and significantly reduce the off-state leakage current of the device.6.Perform noise test on FRHA-SBD,PRHA-SBD and PAA-treated PRHA-SBD.The results show that the noise level of PRHA-SBD is low.This is because the existence of the AlN insertion layer can suppress the two-dimensional electron gas in the channel(2DEG)overflow;the noise level of PRHA-SBD after PAA treatment is the lowest.This is because the density of trap states in the groove area after PAA treatment is greatly reduced,which leads to a decrease in the probability of electrons being captured and released. |
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