Thomas Dalibor

Deep Defect Centers in Silicon Carbide Monitored with Deep Level Transient Spectroscopy

Electrical data obtained from deep level transient spectroscopy investigations on deep defect centers in the 3C, 4H, and 6H SiC polytypes are reviewed. Emphasis is put on intrinsic defect centers observed in as-grown material and subsequent to ion implantation or electron irradiation as well as on defect centers caused by doping with or implantation of transition metals (vanadium, titanium, chromium, and scandium).

Nitrogen donors and deep levels in high‐quality 4H–SiC epilayers grown by chemical vapor deposition

4H‐SiC epilayers grown by chemical vapor deposition were characterized by Hall effect, admittance spectroscopy, low‐temperature photoluminescence, and deep level transient spectroscopy (DLTS). The nitrogen (N) donor activation energies were estimated as 45–65 meV at hexagonal and 105–125 meV at cubic sites from Hall effect investigations in agreement with the data taken by admittance spectroscopy. In low‐temperature photoluminescence, the N bound exciton peaks were dominant, however, free exciton peaks were also observed. DLTS measurements revealed a low concentration of electron traps (∼1013cm−3) for both samples grown on Si and C faces, indicating high‐quality epilayers independent of the substrate polarity.

Radiation-induced defect centers in 4H silicon carbide

Abstract Deep level transient spectroscopy (DLTS) and low temperature photoluminescence (LTPL) were applied to investigate radiation-induced defect centers and their thermal stability in 4H silicon carbide (SiC) epilayers grown by chemical vapor deposition (CVD). The epilayers were implanted with He+ ions and annealed at different temperatures. Several deep defect levels were monitored with DLTS in the 4H polytype. The correlation of these centers with photoluminescence lines is discussed with respect to appropriate annealing steps.

Oxygen in silicon carbide: shallow donors and deep acceptors

Abstract The electrical and optical properties of oxygen (O)-implanted 6H-silicon carbide (SiC) chemical vapor deposition (CVD) epilayers are investigated by Hall effect, admittance spectroscopy, deep level transient spectroscopy (DLTS) and low temperature photoluminescence (LTPL). Two types of O-related centers are found: shallow donors in the energy range of (129–360) meV below the conduction band edge as well as deep acceptor-like defects at EC−480 meV, EC−560 meV and EC−610 meV. For the shallow donors, a certain sensitivity to heat treatments is demonstrated in terms of a decrease of their ionization energies when exposing the O+-implanted epilayers to temperatures at 1650–1800°C. In addition, evidence has been found for the incorporation of O in as-grown 4H-SiC CVD epilayers indicated by the observation of deep O-related defect centers in DLTS spectra.

Thermal capacitance spectroscopy of epitaxial 3C and 6H‐SiC pn junction diodes grown side by side on a 6H‐SiC substrate

The fabrication of 3C‐SiC and 6H‐SiC pn junction diodes, grown side by side on low‐tilt‐angle 6H‐SiC substrates via a chemical vapor deposition (CVD) process, has recently been reported. Admittance spectroscopy and deep‐level transient spectroscopy (DLTS) measurements were made on one of these diodes to compare the defect structure of 3C‐ and 6H‐SiC CVD epitaxial layers grown under the same conditions. The 6H‐SiC layers revealed a single minority carrier level and a deeper broad majority carrier peak. The minority level is due to the boron‐related D center, whereas the broad majority level was identified as a double peak by a DLTS simulation. DLTS measurements on the 3C‐SiC layers revealed only one deep level impurity consistent with the boron‐related D center. Shallow donor levels observed using admittance spectroscopy correspond with the known shallow nitrogen donor in both 3C‐ and 6H‐SiC epitaxial layers. This confirms that both 3C‐ and 6H‐SiC polytypes were simultaneously formed on the same 6H‐SiC sub...

Oxidation of 6H silicon carbide in carbon containing atmosphere

The effect of different oxidizing ambients on the SiC/SiO2 interface has been investigated. We studied the dry oxidation of 6H silicon carbide in O2 with different partial pressures of CO2 as well as in pure CO2 and CO. The density of states at the interface Dit characterized by admittance spectroscopy was found to be correlated with the partial pressure of CO2. We propose that the CO2 partial pressure prevents the outdiffusion of the CO2 which results from the oxidation of SiC leading to a higher Dit with increasing CO2 partial pressure in the oxidizing ambient (Dit (dry O2)=6.3×1010 cm−2 eV−1, Dit(100% CO2)=9.4×1011 cm−2 eV−1).

OBIC studies on 6H-SiC Schottky rectifiers with different surface pretreatments

The influence of different surface treatments on the device characteristics of Schottky rectifiers was investigated. Prior to the formation of Schottky barrier contacts the SiC surface was either thermally annealed in hydrogen, etched using O2 or CF4/Ar/H2 as reactive gases or Ar sputtered. Differences in reverse current densities of several orders of magnitude for different surface treatments were observed. The effective device area was determined by the optical beam induced current (OBIC) technique. The results confirm that the effective device area is given by the area of the metal contact and the additional area of the surface charge induced depletion layer. Our results indicate the importance of an optimized surface treatment in order to control the quality and the area of the surface region for achieving optimum device performance.