New AlGaN/GaN Power Diode Based On Energy Band Modulation Technology

Gallium nitride（GaN）,as a third-generation semiconductor,has a series characteristics that are very beneficial to the development of power electronic devices.Compared with Si devices,GaN devices have higher breakdown electric fields,higher electron mobility,and faster switching speeds,making them more suitable for high-frequency,high-power and high-voltage power electronic systems.Therefore,GaN devices and their preparation technology has received extensive attention and rapid development in the field of power device applications.As one of the basic devices in power electronic systems,power diodes occupy a very important position in the field of power applications.Due to piezoelectric polarization and spontaneous polarization effects in AlGaN/GaN heterostructures,which can generate two-dimensional electron gas（2DEG）with high concentration and high electron mobility,GaN-based Schottky barrier diodes（SBDs）have been subjected to increasing attention.This article innovates from two aspects of structural optimization and process preparation,and proposes a hybrid anode power diode based on an ultra-thin barrier AlGaN/GaN heterojunction.The main content of this article is as follows:（1）First,a new structure of an ultra-thin barrier AlGaN/GaN hybrid anode power diode with MIS gate control（MG-HAD）was proposed.The device structure is based on an ultra-thin barrier AlGaN/GaN heterojunction,and its 2DEG channel has the advantage of natural depletion.By depositing an LPCVD-SiN_x passivation layer on the surface of the barrier layer to regulate the surface energy band,so as to achieve the recovery of two-dimensional electronic gas.The turn-on voltage of the MG-HAD is mainly determined by the intrinsic threshold voltage of the channel 2DEG,it can be flexibly adjusted by changing the thickness of the barrier layer.（2）Through optimization research on its key processes,the intrinsic turn-on voltage(V_ON)as low as 0.31 V determined by the as-grown AlGaN-barrier thickness（4.9 nm）is obtained and the V_ON exhibits excellent uniformity.More importantly,benefit from the MIS-gated hybrid anode structure,the MG-HAD features good thermal stability in reverse blocking capability.The device delivers a substantially low leakage less than 1μA/mm at-300 V at high temperature（HT）up to 200 ^℃,which is more than 100×lower than that in the reference device.And compared with the lateral AlGaN/GaN power diodes published in recent years,our device shows superior reverse blocking characteristics at such a high temperature.Besides,the device exhibits respectably improved dynamic characteristics due to the incorporation of in-situ Si₃N₄ passivation layer and Al₂O₃ gate dielectric with remote plasma pre-treatment（RPP）.When the reverse bias is-175V and the pulse width is 1000ms,the positive current attenuation of MG-HAD is only 20%and the dynamic R_ON only increases by 25%.（3）At the same time,a novel AlGaN/GaN hybrid anode diode（UTB-HAD）was proposed by combining Fin-gate（Fin）structure and ultra-thin barrier structure on the basis of two-dimensional plane MG-HAD.It has the advantages of sidewall conduction and sidewall 2DEG regulation to achieve better forward conduction and reverse blocking characteristics.Based on the preparation technology of three dimensional Fin gate utb-had,the key technologies of electron beam lithography and three dimensional Fin etching were studied.