Comparison of plasma formation in n+p and p+n and TRAPATT diodes

A numerical solution of the plasma-trapping part of the cycle for equivalent `N¿ and `P¿-type TRAPATT diodes shows that, if the conventional criteria for plasma formation are used, the results predicted are contradictory to experimental observations. These calculations, however, do show evidence for a different physical mechanism of plasma formation, with negative electric fields, than has been assumed previously. This mechanism can help explain the observed superiority of `P¿-type diodes. In addition, it is suggested that the material parameters of p¿p+ epitaxial layers may be significantly different for the general run of wafers.