Characterization of two negative-U centers in 4H SiC has been performed using various capacitance transient techniques. Each center gives rise to one acceptor level (-/0) and one donor level (0/+), where the electron ionization energy of the acceptor level is larger than that of the donor level. The two-electron emissions from the two acceptor levels give rise to the previously reported deep level transient spectroscopy peak associated with the so-called $Z_1$ center. Direct evidence for the inverted ordering and temperature dependence studies of the electron-capture cross sections of the acceptor levels will be presented.

• Received 22 June 1998

DOI:https://doi.org/10.1103/PhysRevB.58.R10119