The free hole density and low-field mobility of aluminum-doped 4H-SiC were investigated in the temperature range of 100-900 K, both, experimentally and theoretically. Experimental data for implanted p-type 4H-SiC were compared with theoretical calculations using parameters determined for high-quality epitaxial layers. The deformation potential for intra- and intervalley scattering by acoustic phonons and the effective coupling constant for intra- and intervalley scattering by nonpolar optical phonons were determined. The detailed analysis of the implanted layers with aluminum-targeted concentration ranging from 3.33x10(18) to 10(21) cm(-3) shows that (i) about half of the implanted atoms are electrically active in the SiC lattice, (ii) a systematic compensation of about 10% of the doping level is induced by the implantation process, (iii) two different ionization energies for the aluminum atoms have to be used. Their origin is discussed in terms of inequivalent hexagonal and cubic lattice sites. Finally, the doping dependence of the ionization ratio and Hall mobility are given for non- and weakly (10%) compensated material at 292 K. The maximum achievable mobility for low-doped material in p-type 4H-SiC is shown to be 93 cm(2)/V s at room temperature.

The effect of pressure on electrical transport phenomena has been studied in AlGaN/GaN heterostructures grown on Si substrates. The two-dimensional character of the conducting carriers has been verified with high magnetic field measurements (up to 13 T) at low temperature (T = 1.5 K). The two-dimensional electron gas (2DEG) concentration and mobility were measured as a function of hydrostatic pressure up to 1100 MPa and at different temperatures. The observed pressure changes of the free carrier concentration have been compared with theoretical predictions, taking into account the polarization change in the nitrides and using a fully self-consistent resolution of Schrodinger and Poisson equations.

To model the infrared reflectance spectrum of a conductive multiple layer stack, one needs the plasma frequency and damping parameter of every constitutive material. In this work we show how they can be linked to the resistivity or doping level of the different layers. From a typical application performed in the case of Schottky diode structures, we find that between 1000 and 4000 cm-1, the interference shape of the resulting infrared spectrum is mostly sensitive to the doping level and thickness of the buried buffer layer.

We present a detailed investigation of the influence of oxidation and thinning processes on the in-plane stress in silicon-on-insulator materials. Combining double x-ray diffraction, Fourier transformed infrared and micro-Raman spectroscopy, we show that one can separately evaluate the stress present in the silicon over layer, the buried oxide and the underlying (handle) silicon wafer at any time of a device-forming process.

We report electrical and optical measurements performed on low-doped, n-type 4H-SiC. We show that below a typical carrier concentration of similar to5 10(15) cm(-3) at room temperature, they work in the so-called exhaustion regime from 300 K. The carrier concentration remains constant and the resistivity increases linearly at a rate of 3400 ppm/K from 500 to 800 K. This establishes low doped SiC as a good candidate to produce high performance Hall sensors, working in harsh environment, with a large sensitivity and a low thermal drift.