Effect Of Deep Level Traps On 4H-SiC PiN Devices

Compared with the first and second generation semiconductor materials,the third generation wide band gap semiconductor material silicon carbide(SiC)has a series of excellent characteristics,such as wide band gap,high thermal conductivity,strong breakdown field and high electron saturation drift velocity.Therefore,SiC based devices are favored by scientific research institutions and semiconductor companies all over the world.In SiC based devices,Schottky barrier diodes will cause large leakage current due to the barrier effect,resulting in higher power consumption of the device.Bipolar PiN diodes can obtain lower conduction voltage drop due to the conductivity modulation effect in the forward characteristics,resulting in lower power consumption of the device.At the same time,they have high withstand voltage characteristics in the reverse characteristics and are widely studied.As a photoconductive switch,SiC Based bipolar PiN diodes can turn on and off quickly in high-power switching devices.However,deep level defects in SiC materials can capture photogenerated carriers and reduce the lifetime of minority carriers,thus affecting the photoelectric characteristics of devices.At present,the research of deep level traps in China is still in the preliminary stage,and the relevant information is less.The actual effect of deep level traps on semiconductor devices has not been fully reported.Therefore,the main work of this paper is to study the effect of adding deep level traps on the photoelectric characteristics of devices.In this context,we use deep level transient spectroscopy(DLTS)to test the transient,and obtain the exponential distribution of the transient curve in the appropriate period width.Subsequently,the maximum value of the spectrum obtained from the temperature scanning test is analyzed,and a series of parameters such as the position,concentration and capture cross section of the deep level in the 4H SiC PiN diode are obtained.The position of the trap is analyzed by Silvaco software.The forward and reverse characteristics and temperature characteristics of the deep level trap are simulated by sentaurus software.The changes of the photoelectric characteristics of the device with or without deep level trap are studied.It is found that the deep level trap can capture the carriers from the heavily doped region to the drift region,which leads to the decrease of the device current Due to the contribution of photogenerated carriers,the current of PiN diode increases;after introducing deep level trap,it is found that the trap can also capture photogenerated carriers and cause the current to decrease slightly;in the reverse characteristic,the appearance of deep level trap will produce composite current and increase the current.It is found that the closer the deep level trap is to the Fermi level at equilibrium,the more obvious the effect is.By studying the temperature factor,we can analyze the changes of capture rate,carrier concentration and band gap of deep level trap under variable temperature.By improving the electrode structure and analyzing the front and side irradiation,the influence of the electrode structure on the two irradiation methods is obtained.By changing the thickness of the drift region to improve the withstand voltage of4 H SiC PiN diode,the withstand voltage value is greatly improved.