Research On Simulation Of GaN-Based High-Voltage Diodes

GaN-based power devices have great potential in high-voltage and high-power fields due to their excellent electron mobility,large electron saturation speed and high breakdown electric field.Compared Si-based Schottky barrier diode(Schottky barrier diode,SBD),GaN-based SBD can exhibit better performance in a high voltage power circuit.In theory,GaN-based SBD are ideal for replacing Si-based SBD because of their higher reverse breakdown voltage,lower turn-on voltage and characteristic on-resistance.However,the performance of GaN-based SBD is far from this level,and the breakdown voltage is far from the theoretical value.The high turn-on voltage and characteristic on-resistance cannot meet the low power consumption requirements of commercial products.Therefore,in order to improve the performance of GaN-based SBD,four device structures are proposed,and the electrical characteristics are studied by Silvaco-ATLAS device simulation software.In order to improve the breakdown voltage of the device while reducing the turn-on voltage and characteristic on-resistance,an AlGaN/GaN SBD with partial p-AlGaN cap layer(PPCL)and recessed dual-anode-metal structure(PC-RDA-SBD)is proposed.Firstly,the forward and reverse characteristics of the conventional AlGaN/GaN SBD(C-SBD)are analyzed,and the Al composition of the AlGaN barrier layer in the simulation is determined to be 0.25.Secondly,in order to achieve low loss turn-on of the device without sacrificing the breakdown voltage,recessed dual-anode-metal structure is introduced in the C-SBD,forming recessed dual-anode-metal structure AlGaN/GaN SBD(RDA-SBD).The turn-on voltage of the RDA-SBD is reduced by 73%compared to the C-SBD.Finally,the relationship between the electrical properties of PC-RDA-SBD and the length and thickness of the PPCL is studied,and the size of PPCL was optimized.By using Baliga's Figure of Merit(BFOM),it is determined that the optimum length of PPCL is 5?m and the thickness is 0.2?m.The highest breakdown voltage and the best BFOM value can be obtained at 2461V and 1738 MW/cm~2,respectively.This paper also utilizes high-k passivation layer and composite passivation layer to increase the breakdown voltage of the device.Firstly,the high-k dielectric is applying to the AlGaN/GaN SBD with anode edge termination(AET-SBD)as the passivation layer,forming the AET-SBD with high-k passivation layer(HPT-SBD).By the simulation analysis of the reverse characteristics of the HPT-SBD,it can be seen that the breakdown voltage increases with the relative permittivity and thickness of the passivation layer and the thickness of the passivation layer under the AET region increasing.The breakdown voltage of the HPT-SBD with the relative permittivity of 80 can be obtained up to of 1693 V,while the thickness of the passivation layer and the passivation layer under the AET region are 0.2?m and 25 nm,respectively.Secondly,in order to further improve the breakdown voltage,a low-k dielectric block(LK)is introduced into the passivation layer with the relative permittivity of 30 to form a compound passivation layer,and forming the AET-SBD with compound passivation layer(CPT-SBD).The relationship between the breakdown voltage of the CPT-SBD and the distance between the LK and the AET edge,the length and thickness of the LK are investigated.It also explains the reason for the compound passivation layer improved breakdown voltage.That is,the adoption of the compound passivation layer introduces a new electric field peak at the interface of the high k/low k dielectric,making the channel electric field distribution more uniform,thereby improving the breakdown voltage.Finally,four LKs are used to boost the breakdown voltage of the CPT-SBD to 1950 V.