Mechanisms of changes of hole concentration in Al-doped 6H-SiC by electron irradiation and annealing

The temperature dependence of the hole concentration p(T) in Al-doped p-type 6H-SiC irradiated by 100 or 200 keV electrons is investigated. Since p(T) is unchanged by 100 keV electron irradiation, the threshold displacement energy in SiC is higher than 20 eV. Therefore, 200 keV electrons cannot displace substitutional Si and Al in Al-doped 6H-SiC. Using p(T), two types of acceptor species are detected, and the density and energy level of each acceptor species are determined. By 200 keV electron irradiation, the density (NAl) of the shallow acceptor (i.e., Al acceptor) decreases monotonously with increasing fluence of electrons, whereas the density (NDA) of the deep acceptor initially increases and then decreases. By irradiation with the 1x1016cm-2 fluence of 200 keV electrons, especially, the decrement of NAl is nearly equal to the increment of NDA. By annealing at 500 deg. C, on the other hand, the increment of NAl is close to the decrement of NDA.