Norbert Schulze

Electrical and Optical Characterization of SiC

Three topics are reported in this paper: (a) the determination of a temperaturedependent Hall scattering factor for holes r H,h(T) in 4H-SiC, (b) the detection of shallow Al-related defect centers in Al-doped, p-type 6H-/3C-SiC; these defects are generated either by i mplantation of any ion species or by an oxidation process and (c) the observation of absorption lines in infra red (IR) spectra, which are due to phosphorus donors in 6H-SiC.

Near-thermal equilibrium growth of SiC by physical vapor transport

Abstract Silicon carbide single crystals of the 4H-, 6H- and 15R- polytype are grown by using physical vapor transport (PVT). The crystal growth is performed at conditions where the growth chamber is close to thermal equilibrium. Micropipe-free growth of 6H-SiC on both the C- and Si-face of a 6H-SiC seed is demonstrated. 4H/15R bulk material has been grown on 4H-/15R-seeds, respectively. The growth of 4H-/15R-SiC can not yet be stabilized for the entire boule. Micropipe generation is observed in the neighborhood of polytype transitions, where Raman spectroscopy reveals internal stress. Nitrogen donor concentrations and concentrations of the compensation range from 5.9×10 17 to 1.5×10 18 cm −3 and from 3×10 17 to 6×10 17 cm −3 , respectively. The maximum of the electron Hall mobility is about 200 cm 2 (Vs) −1 (6H–SiC) and 300 cm 2 (Vs) −1 (4H- and 15R-SiC).

Sublimation growth of 4H- and 6H-SiC boule crystals

Abstract The dual-seed-crystal method is developed and used to study the growth of 4H- and 6H-SiC boule crystals by varying particular growth parameters, e.g. the distance between the growth front and the source material and the face polarity of the seeds. A range of values is elaborated for a series of growth parameters, which leads to the growth of single crystals. The grown SiC crystals are electrically and optically characterized.

Controlled growth of 15R-SiC single crystals by the modified lely method

Bulk single crystals of the 15R-polytype of SiC have been grown by the sublimation physical-vapor-transport technique. 15R-SiC crystal growth was stabilized on a 15R-SiC seed using near-thermal-equilibrium growth conditions and a stoichiometric SiC sublimation source material. The polarity of the seed surface is shown to be an important factor in preparation of the 15R-polytype. The dual seed method (simultaneous growth on the Si- and C-face) was employed to demonstrate that 15R-polytype growth occurred only on the Si-face, while 6H- and 4H-polytype growth occurred on the C-face. The incorporation of nitrogen donors and boron acceptors was also shown to be a function of seed polarity, with nitrogen incorporation on the C-face two times that on the Si-face, and boron incorporation on the C-face one-half that on the Si-face.

Identification of dumb-bell shaped interstitials in electron irradiated 6H SiC by photoluminescence spectroscopy

Near displacement-threshold irradiation of 6H-SiC has been perfor med and the damage created studied by low temperature photoluminescence microscopy. Op tical centres are created which have properties consistent with C-C and C-Si dumb-bells.