Christian Peppermüller

PHOSPHORUS-RELATED DONORS IN 6H-SIC GENERATED BY ION IMPLANTATION

Aluminum‐doped 6H‐SiC epilayers were implanted with phosphorus and subsequently annealed in a temperature range from 1400 to 1700 °C. The annealing behavior of implanted phosphorus atoms was studied by the Hall effect, admittance spectroscopy, and photoluminescence. Phosphorus acts as a shallow donor. Two ionization energies of (80±5) meV and (110±5) meV are determined, which are assigned to phosphorus atoms residing at hexagonal and cubic lattice sites, respectively. Assuming first‐order kinetics, the annealing process results in an activation energy of the phosphorus donors of 2.5 eV. A set of four lines at a wavelength of about 420/421 nm is observed in the low temperature photoluminescence spectra; the intensity of these lines increases in parallel with the electrical activation of phosphorus donors by raising the annealing temperature. It is proposed that these lines are phosphorus‐related.

Effects of C or Si co-implantation on the electrical activation of B atoms implanted in 4H–SiC

The influence of co-implantation of C or Si ions on the electrical activation of B acceptors in 4H–SiC was studied by using Hall effect and photoluminescence (PL) investigations. The free hole concentration in B-implanted layers is found to increase due to co-implantation of C and to decrease owing to Si co-implantation. Hot co-implantation of C at 800 °C gives rise to a further increase of the free hole concentration. It is found that the intensity of the PL peak at a wavelength 383.9 nm, which arises from shallow B acceptors [Sridhara et al., Mater. Sci. Forum 264–268, 461 (1998)], is enhanced by the coimplantation of C. These results demonstrate that the electrical properties of B-implanted p-type layers are improved by C co-implantation. The mechanisms, which alter the electrical activation of implanted B atoms due to co-implantation of C or Si, are discussed.

Photothermal ionization spectroscopy of shallow nitrogen donor states in 4H–SiC

Photothermal ionization spectroscopy (PTIS) measurements were carried out on a free-standing, high purity and high quality 4H–SiC epitaxial layer at various temperatures. The two step photothermal ionization process is clearly reflected in the temperature dependence of the photoconductivity. The PTI spectrum at a temperature of 25.6 K exhibits one order of magnitude higher energy resolution than the infrared absorption spectra of 4H–SiC bulk material. It reveals five strong, well resolved electronic transition lines associated with the shallow nitrogen donor. The ionization energy of the shallow nitrogen donor is deduced to be 60.2±0.5 meV based on experimental results. Furthermore, PTI magnetospectroscopy measurements were performed to investigate the symmetry properties of these transitions in Faraday configuration. No linear Zeeman splitting is observed, however, these lines show a diamagnetic shift. It indicates that the excited states of the shallow nitrogen donor are nondegenerate at zero magnetic f...

Hydrogen incorporation in epitaxial layers of 4H- and 6H-silicon carbide grown by vapor phase epitaxy

Abstract The incorporation of hydrogen during vapor phase epitaxy was investigated using secondary ion mass spectroscopy, low temperature photoluminescence, and capacitance-voltage measurements. It was found that hydrogen incorporation is strongly dependent on the concentration of the acceptor dopants aluminum and boron, regardless of changes in the doping concentration caused by varying the concentration ratio between carbon and silicon or the dopant precursor flow. An electrical passivation of the acceptor dopants was found and could be reduced by annealing at temperatures above 1000 °C. At the same anneal temperature hydrogen-related photoluminescence was considerably reduced and the diffusion of hydrogen was detected.

Low temperature photoluminescence measurements on boron- and hydrogen-implanted 6H–SiC

We investigated the low temperature (T<2 K) photoluminescence (LTPL) emission of 6H–SiC samples after implantation of either boron or boron together with hydrogen. After implantation of boron and annealing at 1700 °C, we detected new LTPL emission at 4205 A. After implantation of hydrogen into the boron-implanted and annealed sample, another LTPL emission at 4183 A appeared. We interpret two additional peaks as vibrational modes of the 4183 A emission with energies of 86 and 118 meV.

Hydrogen-, boron-, and hydrogen-boron-related low temperature photoluminescence of 6H-SiC

An investigation of the low temperature (T<2 K) photoluminescence (LTPL) of boron-, hydrogen-, and boron together with hydrogen-doped SiC was done. We used n-type samples of the polytype 6H. After the implantation of boron and annealing at 1700°C, we detected three new LTPL emission lines close to a wavelength of 4205 A. After the implantation of hydrogen into the boron-implanted samples, we detected another single line at 4183 A, while the lines at 4205 A disappeared. In samples with a higher dose of boron, phonon replica of the 4183 A emission line were detected and two vibrational modes affiliated to the defect were identified (86 and 118 meV). The investigation of boron-doped CVD layers revealed intense hydrogen correlated LTPL emission.

Nuclear transmutation doping of 6H-silicon carbide with phosphorous

Abstract Aluminium doped 6H-SiC epilayers on a p + doped 6H-SiC substrate were irradiated with total neutron doses of 9.4 × 10 19 cm −2 , 3.5 × 10 20 cm −2 , and 6.4 × 10 20 cm −2 respectively. A donor species is produced by a nuclear reaction involving the decay of 31 Si to 31 P. The β − activity after irradiation was measured. The samples were subsequently annealed at a temperature range of between 800 and 1800 °C. The annealing behaviour was studied by Low Temperature Photoluminescence (LTPL), Fourier Transform Infrared Spectroscopy (FTIR), Hall-effect, I-V and C-V measurements. The p type 6H-SiC epilayer was transmuted to n-type by an annealing process which resulted in a p-n junction to the p + substrate.