K. Beyzavi et al., OBSERVATION OF SWITCHING ENERGY-DEPENDENCE ON ILLUMINATING BEAM AREA IN THE VSTEP OPTOELECTRONIC SWITCH, IEEE photonics technology letters, 6(2), 1994, pp. 227-230
We have observed a strong dependence of the optical switching energy o
f a p-n-p-n VSTEP device on the area of the illuminated spot. We expla
in the area dependence in terms of a long diffusion time (approximatel
y 1 mus) required for the photo-generated holes to reach a uniform dis
tribution in the depleted p-layer and report results of a carrier diff
usion calculation which supports this conclusion. This effect reduces
the required optical switching energy by as much as a factor of five f
or the devices measured.