▎ 摘　　要

Avalanche multiplication process in avalanche transit time devices results in large number of electrons-hole pairs (EHPs). Therefore, there is considerable temperature rise in the junction. This high temperature than normal operating one, leads to large space charge effects by creating extra space charges. As a result, practical efficiency of transit time devices is below 30%. It is quite important to understand the effects of space charges on device performances. The space charge effect is computationally studied and analysed here for the graphene material based double drift region (DDR) impact ionization and avalanche transit time (GIMPATT) diode. Also, the effect in GIMPATT is compared with IMPATT based on other material like Si, Ge, GaAs, WzGaN, InP, 4H-SiC.