A Comparative Study on the Effect of Optical Illumination on Si1-xGex and Si Based DDR IMPATT Diodes at W-Band

The effect of optical illumination on dc and high frequency performance of si1-xgex based p+pnn+ structured double drift region (ddr) impatt device operating at w-band is investigated and compared with its silicon counterpart. a double iterative computer simulation method based on drift-diffusion model is used to study the dc and small signal properties of the device under dark condition. the same method is used to study the subsequent modification of the dc and small signal parameters due to optical illumination in both top mounted (tm) and flip chip (fc) structures where the composition of photocurrent is altered by shining light on the p+ and n+ sides of the device respectively through optical widow. results show that the dc and small signal parameters of both the si and si1-xgex based ddr devices are affected significantly due to optical illumination. it is observed that the effect of optical illumination is greater in tm structure of both si and si0.5ge0.5 based ddrs compared to fc structure, i.e. electron dominated photo current effect is more prominent than the hole dominated photocurrent in both the devices. but the results significantly indicate that photo-sensitiveness of si1-xgex based ddr impatt is much greater than the si based ddr impatt; which is one of the major findings of this work.