The Simulation And Analysis Of SiGe Fast Switching Power Diode

With the more and more extensive application of power electronics technology, especially with the increasing frequency of main switching device, there have a higher requirement to the power switching diode. The Si p-i-n diode have played an important role in these areas so many years. However, the switching power loss of Si p-i-n diode increase with the switching frequency so that it is necessary to reduce the switching power loss by lifetime control technology which employs lifetime killer such as Au, Pt or radiation to lower the stored charge(Qs). Unfortunately, though the lifetime control technology reduces the stored charge, it increases the forward voltage drop(Vf) and the reverse leakage current(Ir) . Therefore, Si P-i-N diode can't realize a good trade-off in Vf-IrQs. The appearance of SiGe material and SiGe/Si hetero-junction technology have changed this situation. In this paper, the SiGe technology is applied to the performance improvement of power semiconductor devices and the novel structure of SiGe/Si hetero-j unction P+(SiGe)-n"-n+ switching power diodes is presented. On the basis of analyzing the structure mechanism, the device models are set up and the device characteristics are simulated by MEDICI and the optimal design to three key parameters including the thickness of SiGe layer, the percentage of Ge in SiGe layer and the thickness of n" layer is carried out. The 2researching results indicate that the SiGe/Si hetero-j unction switching power diodes have low forward voltage drop, low stored charge, fast and soft reverse recovery and the performance is far better than the similar structure of Si devices. The results of optimal design show that the device with the SiGe layer thickness of 20nm, the 20% Ge in SiGe layer and the n" layer thickness of 10|am has the best performance.