LOW-DOSE IMPLANTATION OF SB IN SI1-XGEX EPITAXIAL LAYERS - CORRELATION BETWEEN ELECTRICAL-PROPERTIES AND RADIATION-DAMAGE

Pure Si(100) and Si1-xGex (x<0.20) layers, epitaxially grown on Si(100 ) substrates, were implanted at room temperature with Sb+ ions at an e nergy of 100 keV and a dose of 10(13) cm(-2) which was found to be bel ow the critical value for amorphization. Spreading resistance profilin g and Hall-effect measurements show that a p-type region was formed in the Si1-xGex alloy layers upon annealing at 500 degrees C, in spite o f the fact that the implanted ion (Sb) is a donor. Only higher-tempera ture anneals transformed the implanted layer into the expected n-type doping. A p-type region was also formed following Xe implantation, ind icating that these results can be attributed to the radiation damage w ithout dependence on the electronic structure of the ion. This phenome non does not exist at all in pure Si. Rutherford backscattering (chann eling) measurements show that the amount of defects formed in the Si1- xGex alloy layer during the implantation process increased with the Ge content, in good agreement with Monte Carlo simulations. These result s can explain the observation that the level of the p-type doping incr eased with the Ge content in the alloys.