| 摘要 |
<p>A governing factor of the switching characteristics of a thyristor device is base layer resistivity, for example in a gate turn-off device, to maximise load current it is preferably low but, the reverse breakdown voltage of the emitter-base junction is improved if the resistivity is high. The invention proposes a modified base layer dopant difusion process in which the dopant source is removed before completion in order that the peak of concentration is diffused-in below the surface so as to produce a graduated resistivity profile which increases nearer the surface. In shorted-emitter thyristors the surface region is masked during subsequent emitter diffusion so that the remaining short columns contain higher resistivity material.</p> |
