Special features of alpha-particle detection with thin semi-insulating 6H-SiC films

The p+-n-n+ structures based on 6H-SiC films grown by chemical vapor deposition on the n+ substrate were irradiated with 8-MeV protons with a dose of 8 x 1015 cm-2. In order to stabilize the material, it was annealed for 10 min at 450 deg. C. As a result, the resistivity of the film was ρ = 5 x 109 Ω cm. The effect of proton irradiation was studied by alpha spectrometry. The 5.77-MeV alpha particles were detected for both reverse and forward bias voltages applied to the structure. The results of the following two modes of detection were compared: (i) a particle traverses the structure without losing much of its energy, and (ii) a particle is stopped in the structure. It is shown that, in the former case and under a forward bias, a signal is formed by a mechanism involving a 'through-conducting channel'. This makes it possible to determine the product of lifetime of electrons by their mobility. The situation in which the particle range R does not exceed the film thickness was analyzed; this situation is typical of spectrometry. It is noted that a decrease in R results in different behavior of the signal for the bias voltages of opposite polarity. Thus, for forward bias, the signal amplitude decreases more rapidly and for larger values of R