Visible light emission from silicon MOSFETS

Abstract

We observe visible light emission from Si MOSFET beyond source-drain breakdown. The intensity as well as location varies with gate bias. For zero gate-voltage ( V g) light is seen from four sides of the drain region. But for positive V g values the location of the light emission shifts to the drain-gate boundary and has a peak in emission intensity at a certain gate bias beyond which it decreases. The initial increase in light intensity is attributed to minority-carrier injection and the decrease at higher gate bias is due to a reduction of lateral field beyond pinch off, which causes a decrease in carrier multiplication. For negative gate-bias, the source-drain breakdown voltage decreases and hence the light intensity increases. A theoretical model for the drain current beyond breakdown is presented and compared with experimental light-intensity curves. The substrate current, which is a measure of the avalanche mechanism by an electron-hole pair generation in the drain depletion region, is measured and compared with light-intensity values.