A study of He+ ion-induced damage in silicon by quantitative analysis of charge collection efficiency data

The ion damage is responsible for the progressive reduction of the collection efficiency of a semiconductor device in Ion Beam Induced Charge (IBIC) measurements. This effect was studied by irradiating a silicon n(+)-p diode with a 1.85 MeV He+ microbeam at very low fluences less than or equal to 5 x 10(9) ions/cm(2) and measuring the decrease of charge pulse height vs ion fluence. The experimental results can be described by a model, which represents the region of maximum damage as an interface with given carrier recombination velocity v(s). The model assumes that the ion fluence affects v(s), but not the bulk minority carrier diffusion length. The comparison between experiment and theory yields an approximately linear relationship between ion fluence and v(s); this yields a value of about 7 for the average number of recombination centers produced by a single He+ ion. (C) 1998 Elsevier Science B.V.