Large-signal(L-S) characterizations of double-drift region(DDR) impact avalanche transit time(IMPATT)devices based on group III–V semiconductors such as wurtzite(Wz) GaN, GaAs and InP have been carried out at both millimeter-wave(mm-wave) and terahertz(THz) frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation(NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials(i.e. GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies. Large-signal (LS) characterizations of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III-V semiconductors such as wurtzite (Wz) GaN, GaAs and InP have been carried out at both millimeter-wave A LS simulation technique based on a non-sinusoidal voltage excitation (NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the LS properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, ie Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials (ie GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter both mm-wave and THz frequencies.