Breakdown Mechanism And New Structure Of GaN Based Power Diode

GaN material,with wide-bandgap,has excellent material properties,is widely used in power semiconductor devices.Related researches on GaN-based power diodes at home and abroad show that the current GaN-based power diodes have the problems of junction edge electric field concentration and uneven electric field distribution,which severely restrict the withstand voltage improvement of GaN-based power diodes.This article has conducted in-depth research on GaN-based power diodes.The research content and research results are summarized as follows.At first,this paper proposes a new structure of GaN-based power diodes(TCD-TGD),which use the compound dielectric to modulate the electric field of drift region.Research results indicates,the breakdown voltage of TCD-TGD is 5360 V,the BFOM is18.78 GW/cm~2,and the average breakdown electric field is 3.35 MV/cm.Through the study of the switching characteristics of the structure,the reasons for the increase of the reverse recovery time of the diodes were found to be the parasitic capacitance introduced by the compound dielectric and the influence of the compound dielectric structure on the diode barrier capacitance.Finally,by combining the vertical field plate,the electric field concentration at the edge of the junction is effectively suppressed,and the breakdown voltage of the device is further improved.Secondly,electrical characteristics of AlGaN/GaN heterojunction Schottky diode were studied.The study found that when the SBD is forward-conducted,the main forward transport mechanism in the linear region has two types:TE mechanism and TU.The TE mechanism gradually dominates with the increase of temperature.When SBD is reverse biased,the dominant mechanism of leakage current changes from FP effect to FN effect with the electric field increasing.Next,The electrical characteristics of two SBDs with anode metals of Ni/Au and Pt/Au were tested,and the effective SBH calculated by the two differed by about 0.1 eV.Due to the influence of the surface state,the Pt/Au alloy does not form a higher SBH.As the chemically more active Ni metal has better adhesion on the surface of GaN materials,Ni/Au-SBD forms a better quality Schottky contact,and the leakage current is reduced by 2 orders of magnitude compared with Pt/Au-SBD.Finally,the SBD with a passivation layer and the SBD without passivation are compared.The CV test results of the two at V_a=0 V show that the mobility and two-dimensional electron gas concentration of passivated SBD have decreased due to the influence of the AlGaN/GaN interface acceptor trap.After passivation,the magnitude of the SBD leakage current increased by about 3 orders of magnitude,which is due to the interface charge at the Six N/GaN interface introducing a new leakage path in the diode.