W. J. Choyke

Localized vibrational modes of a persistent defect in ion-implanted SiC☆

Abstract The low-temperature luminescence spectrum of an intrinsic defect in ion-implanted cubic SiC reveals a number of high-energy localized modes. One has an energy of 164·7 meV, equivalent to the highest lattice frequency in diamond, and far above the 120·5 meV lattice limit of SiC. A carbon di-interstitial is a plausible model for the defect, which appears after a 1300°C anneal, and persists after a 1700°C anneal.

Refractive Index and Low-Frequency Dielectric Constant of 6H SiC

The ordinary refractive index of 6H SiC has been measured from 2.43 μ (0.51 eV) to 0.336 μ (3.69 eV), using the transmission interference fringes of thin plates. Thibault’s data in the visible were used to normalize the dispersion curve. The index goes from 2.530 at 0.51 eV to 2.868 at 3.69 eV. The residual-ray and interband contributions to the index are evaluated. The extrapolated interband index plus residual-ray contribution yield a low-frequency dielectric constant of 9.8, compared with a measured 10.2. As possible reasons for the disagreement, four allowed but unreported infrared transitions are considered.

Impurity Bands and Electroluminescence in SiC p‐n Junctions

A study of the electroluminescence of certain SiC p‐n junctions, between 77°K and 830°K, and over a range of 104 in current density, has been used to verify and to extend a 3‐part model (P−N*−N) of the junctions derived from electrical measurements. The electroluminescence, due to recombination in N*, consists of two parts, which may be called impurity luminescence and intrinsic recombination radiation. At low temperatures (≥200°K) only the former is present. Several effects of impurity banding on the electroluminescence can be predicted, and some of these have now been observed. The most striking of these effects is the ``Fermi‐level emission edge in the low‐temperature spectra, an edge which moves to higher energies with increasing current density because of the impurity band injection of electrons. The predominance of impurity band injection at low temperatures excludes the possibility of intrinsic recombination radiation. At higher temperatures, however, electron injection is by way of the conductio...

Magneto-Optical Measurements on H-Implanted 6H SiC

Magneto-optical measurements were made at 4.2°K on two kinds of luminescence spectra found in H-implanted 6H SiC. Both spectra are attributed to the same center, an H atom bonded to a C atom at a Si vacancy. One spectrum (called secondary) is due to exciton recombination at a charged center, and its magnetic response is explained by effective-mass theory with gh = 2.8 and ge = 1.8. The other spectrum (called primary) is due to recombination of an exciton strongly bound to the neutral center. Its magnetic splittings are explained by a strong-exchange model, with a singlet level 6.5 meV above the triplet level.