Papers by Keyword: PICTS

Abstract: Deep level transient spectroscopy (DLTS) and photo induced current transient spectroscopy (PICTS) are commonly used methods for the identification semiconductor impurities and defects. In this paper, a measurement system of DLTS and PICTS has been developed by LabVIEW. A series of different instruments construct this systems hardware (signal generator; current amplifier; capacitance meter; oscilloscope,etc.) while software is also easy to program by LabVIEW. This system demonstrates high generality for both DLTS and PICTS, and data acquired can be stored or read in computer. By contrast, it is much lower cost comparative to commercial DLTS or PICTS system. Testing result of silicon P+N junction coincides with semiconductor theory research.

Abstract: We measured the temperature dependence of the electrical resistivity for two high-purity undoped 6H-SiC bulk wafers with resistivities of 1.5103 cm and 8.3108 cm at room temperature. We also characterized the deep levels affecting the semi-insulating property by current deep level transient spectroscopy (I-DLTS) and photo induced current level transient spectroscopy (PICTS) measurements. The activation energies of the resistivity were 0.11 eV and 0.59 eV for the samples with lower and higher resistivities, respectively. In I-DLTS and PICTS spectra, the sample with lower resistivity shows a donor level at Ec0.17 eV and two acceptor levels around Ec0.40 eV, while the sample with higher resistivity shows acceptor levels at Ec0.77 eV and Ev+0.46 eV. We calculated the temperature dependence of the resistivity with a model considering one donor level and one acceptor level based on parameters from I-DLTS peaks. We reproduced the experimental results only for the sample with lower resistivity. The acceptor level near the valence band needs to be considered to explain the resistivity for the sample with higher resistivity.

Abstract: Undoped 6H- and 4H-SiC crystals were grown by Halide Chemical Vapor Deposition (HCVD). Concentrations of impurities were measured by various methods including secondary-ion-mass spectrometry (SIMS). With increasing C/Si ratio, nitrogen concentration decreased and boron concentration increased as expected for the site-competition effect. Hall-effect measurements on 6H-SiC crystals showed that with the increase of C/Si ratio from 0.06 to 0.7, the Fermi level was shifted from Ec-0.14 eV (nitrogen donors) to Ev+0.6 eV (B-related deep centers). Crystals grown with C/Si > 0.36 showed high resistivities between 1053 and 1010 4cm at room temperature. The high resistivities are attributed to close values of the nitrogen and boron concentrations and compensation by deep defects present in low densities.