He+ ion damage in 4H-SiC studied by charge collection efficiency measurements.

The nuclear microprobe facility of the Italian National Laboratories of Legnaro was used for an Ion Beam Induced Charge Collection (IBIC or IBICC) experiment which measured the charge collection of a 4H-SiC Schottky diode irradiated with 2 MeV He+ at increasing doses. The experiment was arranged so as to obtain a statistics of about 1400 events per each He+ ion from the 1(st) to the 500(th) one on the ion microprobe spot (1.5 x 1.5 mum(2)). These figures correspond to He+ fluence values in the range 10(7)-10(11) ions/cm(2). The charge collection of the diode was almost constant from the 1(st) to the 10(th) He+ ion, i.e. up to a fluence of 10(9) ions/cm(2), and then monotonically decreased for the subsequent ions. The SiC device collection efficiency was modelled by representing the electrical effects of the damage produced by ions as a planar interface region of given carrier recombination velocity at the depth of the damage peak. Experimental and computed data scale one to the other assuming that the interface recombination velocity and He+ fluence are linearly related.