The effect of electron bombardment on optical properties of n-type silicon

The production of p–n junctions and polar transistors in silicon to small scale lengths may be possible by plasma and electron beam techniques using the sub-threshold change of n-silicon into p-silicon by electron beam and its reversion at higher electron beam intensities. As a first step, in this study, experimental observation of the effect of electron beam on optical properties of n-type silicon samples is described. Electron bombardment with the energy of 20 keVand different doses in the range of 1016 to 1019 electron/cm2 has been carried out. Use was made of a new design of an electron beam gun as described in details, using a helium obstructed discharge of a concave cold cathode. Optical properties of irradiated samples were determined by a UV–vis–NIR spectrophotometer. The results show an increase in the longer wave length than the fundamental band gap absorption with increasing electron dose