IMPLANTATION OF PHOSPHORUS AND ARSENIC IONS IN GERMANIUM

In order to determine the experimental conditions that are necessary to produce a shallow donor type layer in germanium, 20 keV phosphorous ions and 30 keV arsenic ions have been implanted at different doses into germanium samples. The resulting crystalline damage and its annealing upon heat treatment have been investigated by means of ellipsometry measurements and Rutherford backscattering spectrometry. Depending on the initial damage level most of the crystalline defects anneal out in the temperature range 200-400-degrees-C. However residual defects remain up to about 450-degrees-C, independent of the implanted dose. As these defects behave like acceptors centers and compensate the electrical activity of the implanted phosphorous or arsenic atoms, they must be completely eliminated before a good donor type contact can be obtained.