Simulation of a near infrared light-activated 4H-SiC Darlington transistor switches

The novel near infrared light-activated Darlington heterojunction transistor power switch made of SiC has been proposed, in which SiCGe/SiC pn is employed to produce a base current by means of optical illumination. By using two-dimensional numerical simulation MEDICI, the SiCGe/SiC photodetector can be triggered by a near infer-red laser beam if the composition parameters of the Sil-x-yCxGey have been chosen properly. Performance of the near Infrared light-activated power switch was simulated, which has shown that the light-activated device has very good switching characteristics at 0.85μm for optical intensity of 1.0 Watt/cm2. Based on our simulation results, the distribution of current density predicts that the auxiliary transistor is turned on at first by a low density of photocurrent and then the main transistor is turned on. The collector current of the device in the on-state is concentrated in a region underneath the main emitter.