Formation of donors in germanium–silicon alloys implanted with hydrogen ions with different energies

The distributions of hydrogen-containing donors in Ge$_{1-x}$Si$_{x}$ (0 $\le x\le$ 0.06) alloys implanted with hydrogen ions with an energy of 200 and 300 keV and a dose of 1 $\times$ 10$^{15}$ cm$^{-2}$ are studied. It is established that, at the higher ion energy, the limiting donor concentration after postimplantation heat treatment (275$^\circ$C) is attained within $\sim$30 min and, at the lower energy, within $\sim$320 min. In contrast to donors formed near the surface, a portion of hydrogen-containing donors formed upon the implantation of ions with the higher energy possess the property of bistability. The limiting donor concentration is independent of the ion energy, but decreases from 1.3 $\times$ 10$^{16}$ cm$^{-3}$ to 1.5 $\times$ 10$^{15}$ cm$^{-3}$, as the Si impurity content in the alloy is increased from $x$ = 0.008 to $x$ = 0.062. It is inferred that the observed differences arise from the participation of the surface in the donor formation process, since the surface significantly influences defect-formation processes involving radiation-induced defects, whose generation accompanies implantation.