Limitations on the use of platinum in power devices

There is growing interest in the use of platinum as a lifetime control element in bipolar devices. This paper discusses key differences between the conventionally used gold lifetime killer and platinum, with particular emphasis on high injection effects and high temperature effects. It is shown that generation at platinum impurity centers is orders of magnitude less than at gold centers, allowing improved high temperature leakage. It is also shown that minority carrier lifetime decreases with increasing current when platinum is used, causing forward dissipation difficulties. No such effect has been seen with gold. Platinum can provide improved turn-on performance and high temperature leakage in devices which are switched so rapidly that the turn-off is governed mainly by the high injection lifetime. When the switching wave form involves low injection recombination tails, the shorter high injection lifetime leads to prohibitively high forward dissipation, and gold is preferable to platinum.