Research of the Ga and Al double-impurity doping technique for making fast switching thyristor

Abstract

We describe a novel technique for producing the p-type semiconductor. The homogeneous impurity doping of Ga and Al in the n-type silicon wafer is achieved by means of the combination of two technical processes namely aluminum emulsion coating and vaporizing Ga. This Ga-Al double-impurity doping technique, as well as its effect on the quality of the produced semiconductor devices, is investigated theoretically and tested in practice. The principle of the doping technique is also discussed in detail. By using SRP, four-probe needle and thyristor analyzer, we have examined the Ga-Al impurity concentration distribution within the silicon wafer, thin layer resistance RS, and other useful parameters of the fast switching thyristors made by this technique. The turn-off time of the fast switching thyristors, toff is 31.2—38.6 μs, turn-on time ton is 4.6—5.9 μs, and the forward voltage drop VTM measured is 1.9—2.1 V. Both experiment and some real applications indicated that this technique may obviously improve the semiconductor device in the overall performance, the electrical parameter uniformity and the end product rate. It provides a feasible technique for making fast switching thyristors.