Photoluminescence of H- and D-implanted4HSiC

A new luminescence center in $4H$ SiC is efficient during the first minute of exposure to the uv exciting light at 4 °K, but soon fades out, only to be fully restored by a room-temperature anneal. The center is an H atom bonded to a C atom at a Si vacancy and is formed by H implantation followed by annealing. Two such centers are formed at two inequivalent $4H$ sites, and only one is quenched. The other remains as an efficient luminescence center, as do both corresponding centers in D-implanted $4H$ SiC. The quenching mechanism is thought to be a change in the charge state of the center, the luminescence being attributed to exciton recombination at a neutral center. A $g$ value of 4 is derived from magneto-optic measurements of the exciton in the ground state, indicating that the electron and hole spins are parallel. The $4H$ luminescence spectrum is similar in many ways to the primary spectrum of H-implanted $6H$ SiC. The secondary spectrum found in polytype $6H$ is absent from $4H$. A doublet structure due to the presence of axial and nonaxial centers is described.