Jean Camassel

Activation of aluminum implanted at high doses in 4H–SiC

We report an investigation of the electrical activation of aluminum implanted at high dose in 4H–SiC. We show that at reasonably high temperature implantation and annealing conditions, one activates about 37.5% of the implanted species. Of course, the final (concentration-dependent) activation ratio differs slightly from this average value but varies only between 0.5 and 0.25 when the targeted concentration increases from 3.33×1018 to 1021u200acm−3. Provided a standard mobility can be maintained, this results in fairly low sheet resistance. The best (lowest) value obtained in this work is 15 mΩu200acm at 700 K (95 mΩu200acm at room temperature) for a 190-nm-thick layer implanted with 1021u200aatomsu200acm−3. In MESA-etched p–n junctions with a 100 μm diameter, this resulted in a typical on-resistance of 1.5 mΩu200acm2, mainly limited by the substrate and n− epitaxial layer.

Electrical transport properties of aluminum-implanted 4H–SiC

The free hole density and low-field mobility of aluminum-doped 4H–SiC were investigated in the temperature range of 100–900K, 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 3.33×1018to1021cm−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...

Free electron density and mobility in high-quality 4H–SiC

The free electron density and low-field electron mobility of 4H–SiC is examined in the temperature range 35–900 K. In good samples the electron density is constant in the temperature range 300–900 K, which offers interesting possibilities for high temperature sensor applications. On the best sample an experimental electron mobility of 12u200a400u200acm2/Vu200as at 50 K is found. A complete description of the temperature dependence of the electron density and mobility is given. We take into account the effects of the two inequivalent lattice sites as well as the valley–orbit splitting of the ground state at the hexagonal sites. The dependence of room-temperature mobility on electron concentration is established, described theoretically and compared with the results obtained by different authors.

Thermal stability of InGaAs/InGaAsP quantum wells

We report a cross investigation of the effect of interdiffusion on the photoluminescence and Raman spectra of a single quantum well of InGaAs (80 A wide) sandwiched between two large InGaAsP barriers. First, we investigate the blue shift of the recombination line (2 K) after annealing at 650 and 750u2009°C from 15 min to 2 h. We assume one single diffusivity coefficient for all atomic species (i.e., conservation of the lattice matching after annealing) and deduce the amount of intermixing through a model calculation. We find average diffusivity coefficients D=9.5×10−3 A2u2009s−1 and D=2×10−1 A2u2009s−1 at 650 and 750u2009°C, respectively. This agrees well with previous measurements reported for the parent system InGaAs/InP and supports an activation energy EA=2.54 eV. Next we investigate, on the same series of samples, the change in phonon frequency associated with the GaAs longitudinal‐optical‐like mode in the active InGaAs layer. To connect quantitatively the change in wave number with the change in arsenic composition...

Structural, optical and electrical properties of state of the art cubic SiC films

Abstract The structural, optical and electrical characteristics of commercially available cubic (β)-SiC films grown on 〈001〉 silicon waters were reported. For the structural characterization, combined plane view and cross-section transmission electron spectroscopy observations were made. For the optical investigations, low-temperature photoluminescence (2 K) and room temperature Raman and infrared spectra were measured. For the electrical characterization, Hall effect and resistivity measurements were performed in the temperature range 15–500 K.

Optical investigation methods for SiC device development: application to stacking faults diagnostic in active epitaxial layers

We present a review of the different optical techniques that can be used to investigate the presence of as- grown and/ or process- induced stacking faults ( SFs) in 4H - SiC epitaxial layers. A SF is always a finite admixture of different polytypes, and we begin with a brief review of the systematic of SiC polytype structure and electronic properties. Next, we discuss the optical signature and compare with the results of several model calculations, taking successively into account the effect of valence band offset, internal polarization and non-homogeneity of the potential well. Finally, we consider cathodo-luminescence and micro- photoluminescence techniques and show that, in both cases, some screening of the built- in electric field can be achieved.

Investigation of porous silicon as a new compliant substrate for 3C-SiC deposition

Investigation of porous silicon as a new compliant substrate for hetero-epitaxial deposition of 3C-SiC on silicon has been performed. The resulting layer has been analyzed in terms of X-ray diffraction, infrared reflectivity, micro-Raman scattering and low temperature photoluminescence experiments. From the results, intermediate properties between 3C-SiC deposited on bulk silicon and 3C-SiC deposited on SIMOX have been found.

Quantum Hall effect in bottom-gated epitaxial graphene grown on the C-face of SiC

We demonstrate that the carrier concentration of epitaxial graphene devices grown on the C-face of a SiC substrate is efficiently modulated by a buried gate. The gate is fabricated via the implantation of nitrogen atoms in the SiC crystal. The charge neutrality point is observed close to gate voltage zero, and graphene can be populated by either holes or electrons down to low temperature (1.5u2009K). The hole concentration is hardly tuned by the gate voltage, possibly because of interface states below the Dirac point. A remarkably large quantum Hall plateau is observed for electrons.

Role of SIMOX defects on the structural properties of β-SiC/SIMOX

Abstract We have investigated the role of microscopic defects, which usually are present at very low density in the thin silicon overlayer (SOL) of SIMOX wafers, on the final structural properties of β-SiC grown on top of this material. To modify the defects density we have used different wafers with SOL thickness ∼150, 100 and 50 nm, respectively. After SiC deposition, we have found that the density of defects (mainly holes running through the SiC films and underlying cavities) follows, roughly speaking, the concentration of initial defects in the SOL. Taking into account the diffusion of atomic species and the different possible chemical reactions, the microscopic mechanism of holes and cavities formation is discussed.

Gas source molecular beam epitaxy of β-SiC on Si substrates

The growth of β-SiC films on Si(100) substrates using C 2 H 2 gas and Si solid sources in a molecular beam epitaxy system has been investigated. Different C 2 H 2 and Si fluxes as well as different substrate temperatures have been used. The growth was performed at two steps : the initial optimal carbonisation step followed by the MBE growth with simultaneous supply of Si molecular and C 2 H 2 gas beams. The films were analysed using reflected high-energy electron diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy. Thin (< 0.1 μm) single crystalline SiC was grown at 980°C while 850°C was sufficient for the carbonisation of the Si surface. Films thicker than 0.1 μm are partially polycrystalline.