Surinder Krishna

Optimization of recombination levels and their capture cross section in power rectifiers and thyristors

Abstract Single level recombination statistics have been used to determine the influence of lifetime on the characteristics of power rectifiers and thyristors. It is shown that the ratings of rectifiers can be optimized by maximizing the ratio of the high level to the low level lifetime. An optimization criterion relating the recombination center location to its capture cross section ratio for holes and electrons is derived. The relationship is found to be a function of temperature but not dependent upon the resistivity of the base material. In the case of thyristors it is shown that the leakage current must also be considered in the optimization procedure. This leads to a criterion which relates the recombination center location to the resistivity and the capture cross section. In addition, presently used techniques of gold diffusion and electron irradiation are shown to produce levels which fit poorly into the optimization scheme. The work in this paper points out the need to gather more information regarding the energy levels and capture cross sections of other impurities in silicon.

“GAMBIT: GAte Modulated BIpolar Transistor”

Abstract A planar, interdigitated, integrated device structure is described whose characteristics show a voltage controlled negative resistance between two of its terminals. This negative resistance can be controlled by the applied bias to a third terminal. Devices have been fabricated with this structure to achieve negative resistance values ranging from a few hundred thousand ohms down to less than a hundred ohms. The physical mechanisms that give rise to this negative resistance are described and a dc analysis of its behavior is presented. The analysis shows excellent agreement with the observed device characteristics.

Second Breakdown in Power Transistors Due to Avalanche Injection

This paper studies the subject of reverse bias second breakdown both experimentally and analytically. It is seen that there is excellent correlation between theory and experiment. The conclusion of this investigation is that avalanche injection is the triggering mechanism. Further, the filamentary currents that result from this can in most cases result in device failure. It is also concluded that under fixed circuit conditions, the reverse bias second breakdown potential of a transistor is completely specified by the single parameter, Vp, which is the voltage necessary for avalanche injection.

Second breakdown in power transistors due to avalanche injection

Second breakdown in power transistors continues to be an actively discussed subject. Although there is general agreement that the lateral thermal instability model adequately explains forward bias second breakdown, it fails to explain the reverse bias failure mechanism. The thermal initiation and electrical initiation processes have been successful in explaining only some aspects of this phenomena. This paper studies the subject of reverse bias second breakdown both experimentally and analytically. It is seen that there is excellent correlation between theory and experiment. The conclusion of this investigation is that avalanche injection is the triggering mechanism. Further, the filamentary currents that result from this can in most cases result in device failure. It is also concluded that under fixed circuit conditions, the reverse bias second breakdown potential of a transistor is completely specified by the single parameter Vpwhich is the voltage necessary for avalanche injection.