Deep Level Defects Related to Carbon Displacements in n- and p-Type 4H-SiC

Abstract

We have investigated the electrically active deep level defects in p- and n-type 4H-SiC after low energy electron irradiation. Intrinsic defects were created by irradiation with 200 keV electrons, with energy sufficient to move only the carbon atoms in SiC lattice. Defect spectra were compared between the p- and n-doped samples prepared under identical irradiation conditions. We probed both conduction and valence band sides of the band-gap by using capacitance transient techniques with electrical and optical trap filling. We have found that the defect spectrum in the p-type epilayers differs significantly from the n-type. The Z1/Z2, EH1 and EH3 electron traps which are usually present in irradiated n-type material could not be detected in p-type samples. An electron trap at 1.6 eV below the conduction band edge is present in both n- and p-type samples at the same energy position and with similar concentration, therefore it is probably related to the same type of defect. We have also found a new hole trap in p-type epilayers at energy EV + 0.66 eV.