A. tunnel B. Shottky C. Shockley D. DIAC 3. 1. IMPATT diode is fed at the maximum current densit y, which is exactly the case at the pulsed-mode operation. IMPATT oscillation also occurs in helium-radiated, locally carrier lifetime controlled devices [5]. D. Increase the current through the diode. employed and a number of theo- retical studies have been made to try and achieve an optimized design.