Silicon Based Light Emission by Avalanche Breakdown of Shallow p+/n+ Junctions

The objective of this study was to develop and demonstrate a technology for producing optical signals on a VLSI chip using only standard silicon processing techniques. The design of the process requires shallow p+/n+ junctions to minimize the high absorption inherent in silicon for λ< 8SOnm and to obtain low reversed biased voltages for avalanche break down of the p+/n+junction due to impact-ionization. The effects of doping and device geometry on the visible luminescence of reverse biased Si p+In+ junction diodes has been investigated. Each diode designed has a unique design incorporating sharp edges that promote high fields that aid the onset of break down. The p+ doping was varied while other processing parameters were held constant. All vertical junction diodes had excellent diode characteristics but no light emission was observed. Lateral junction diodes had typical reverse breakdown voltages of between 6 and 7 volts while certain devices of set geometry broke down rather sharply at 4 volts with light emission. Intensity and breakdown characteristics seemed to correlate with magnitude of p+ dose and device geometry.