Abstract: Minority carrier (hole) lifetime investigations are conducted on identical 6H-SiC p+-n structures by electrical (reverse recovery, open circuit voltage decay) and optical (time-resolved photoluminescence) techniques. The p+-n diodes are fabricated by Al implantation. Depending on the particular analysis technique, the lifetime is determined either electrically in different regions of the p+-n diode or optically in the n-type 6H-SiC epilayer and results, therefore, in different values
ranging from ≈10 ns to 2.5 µs.
Abstract: Specific on-resistance Ron estimated from current density-voltage characteristics of
Schottky diodes on thick layers exhibits variations from tens of mW.cm2 to tens of W.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with the temperature was observed and its dependencies of T–1.3 and T–2.0 for moderately doped and low doped samples respectively were estimated. From deep
level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on dependence of on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism thus resulting in high Ron.
Abstract: The effects of the Si/H2 ratio on the growth of the epitaxial layer and on the epitaxial
defects was studied in detail. A large increase of the growth rate has been observed with the increase of the silicon flux in the CVD reactor. Close to a Si/H2 ratio of 0.05 % silicon nucleation in the gas phase occurs producing a great amount of silicon particles that precipitate on the wafers. The epitaxial layers grown with a Si/H2 ratio of 0.03% show a low defect density and a low leakage current of the Schottky diodes realized on these wafers. For these diodes the DLTS spectra show thepresence of several peaks at 0.14, 0.75, 1.36 and 1.43 eV. For epitaxial layers grown with higher values of the Si/H2 ratio and then with an higher growth rate, the leakage current of the Schottky diodes increases considerably.
Abstract: The fabrication process and the spectral properties of gratings for the infrared wavelength region on the basis of 3C-SiC layers grown by CVD on (100) oriented Si substrates are demonstrated. The formed 3C-SiC gratings on Si support two phonon polaritons as a function of the geometrical properties excited between 10.3 and 11.4 µm. They appear as a dip in the transmission spectrum. A third minimum in the transmission spectrum is caused by the substrate – grating interaction. The obtained resonances were polarization sensitive, i.e. they appeared only under TMpolarized illumination.
Abstract: Structural defects in SiC crystals were investigated and 4H-SiC pin devices were
characterized by micro-Raman scattering and photoemission. With the experimental set-up presented, defects could be successfully detected in SiC crystals but stacking faults could not be detected with micro-Raman scattering, although they could be detected by photoemission. Residual stress could be evaluated in 4H-SiC devices, as well as the temperature increase associated with the devices powering. A good correlation was found between the characterization techniques used:
micro-Raman scattering and photoemission.
Abstract: Temperature-dependent Hall effect investigations in the channel of lateral 3C-SiC
LDDMOSFETs with nitrogen(N)-implanted source/drain regions are conducted. The free electron concentration and the electron Hall mobility are independently determined. A maximum electron Hall mobility of 75 cm2/Vs is observed. The gate oxide withstands electric field strengths up to 5 MV/cm. A high density of interface states of a few 1013 cm-2eV-1 close to the 3C-SiC conduction band edge still lowers the performance of the MOS device.
Abstract: Several SiC bulk crystals were grown with erbium and ytterbium as doping materials.
Erbium contents determined by secondary ion mass spectroscopy (SIMS) ranged from 1.2 · 1014 cm-3 to 1.04 · 1015 cm-3, while ytterbium contents were below SIMS detection limit. Photoluminescence (PL) investigations of the characteristic 4f-4f-transition lines revealed a reduced luminescence yield in highly nitrogen and aluminum co-doped samples. Also, samples without intentional
co-doping grown on the C-face showed less luminescence intensity than those grown on the Si-face. A stabilizing effect of erbium doping on the 4H polytype was observed.
Abstract: Recently, a systematic comparison of SIMS measurements with LTPL (Low Temperature Photoluminescence) spectra led us to propose a straightforward empirical calibration of the LTPL intensity versus Al content in 4H-SiC samples. In the present work we analyze the effect of the LTPL excitation power on the intensity of the Al-related features. We examine the influence of the excitation conditions on the calibration curve and determine the limitations of the method.
Abstract: The concentration of nitrogen and phosphorous in SiC bulk material and epitaxial layers was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The advantage of TOF-SIMS of acquiring a complete mass spectrum in a single run was used to identify the most sensitive atomic ion or ionic cluster for the selected element to be monitored. For the investigation
of N with its intrinsic low ionization yield the use of a Cs containing cluster ion is necessary. Selection of a CNCs2 + cluster allows to reach a detection limit of about cN,min » 5×1016 cm-3. In the case of P the elemental ion was used. However, the adjacent mass of 30SiH influences the P peak as well as its background and has to be suppressed. This can be achieved by limiting the residual gas
re-adsorption during the measurement resulting in a detection limit of about cP,min » 5×1015 cm-3. These measurement parameters were used to investigate a single crystal SiC bulk sample grown by the modified Lely method with intentional P doping and an N doped epitaxial SiC layer sample.