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Received 18/12/2011, accepted 07/01/2012, online 10/01/2012 The high frequency performance limitations of Si, GaAs and InP IMPATT devices based on avalanche response time is investigated in this paper. Drift-diffusion model is used to design SDR IMPATTs based on Si, GaAs and InP at different millimeter-wave and sub-millimeter-wave frequencies and corresponding avalanche response times and associated avalanche delay as well as transit times are calculated. Results show that the high frequency limits of GaAs and Si IMPATT devices are 147 GHz and 500 GHz respectively. It is observed that InP IMPATTs are highly suitable for operation at higher mm-wave and terahertz frequencies due to smaller value of avalanche response time of InP as compared to Si and GaAs