Two electron traps—A2 and A3—produced in n-type silicon by 1.5-MeV-electron irradiation are characterized by deep level transient spectroscopy. Activation energies of trapped majority carriers and capture cross sections for majority carriers at these levels are reported. From their production rates and annealing behaviors, they have been identified as different charge states of the same defect. Detailed annealing studies show that their annealing kinetics is first order with an activation energy of 1.47 eV. It is suggested that the defect is the divacancy and that dissociation is the likely process for its removal in these devices.
Temperature dependent Hall effect, optical admittance spectroscopy, and optical absorption measurements of semi-insulating bulk 4H-SiC are reported. Both intentionally vanadium doped material and commercial grade semi-insulating material were investigated. The carrier concentration versus inverse temperature results from Hall effect measurements up to 1000 K indicated the samples were dominated by one of two deep levels near midgap. In addition to the deep donor level of substitutional vanadium, E c Ϫ1.6 eV, we observed another level at E c Ϫ1.1 eV in some samples, indicating that levels other than the vanadium donor can pin the Fermi level in semi-insulating SiC. Optical admittance measurements on the semi-insulating material indicate the presence of levels at E c Ϫ1.73 and 1.18 eV that were previously observed in conducting samples with this technique and we attribute these levels to the same defects producing the 1.1 and 1.6 eV levels seen by Hall effect. Secondary ion mass spectroscopy measurements of dopant and impurity concentrations are reported. Even though vanadium is present in all of these samples, along with other impurities we are at present unable to definitively identify the 1.1 eV level.
A new technique to decompose closely spaced interface and bulk trap states using temperature dependent pulsewidth deep level transient spectroscopy method:An application to PT/CdS photodetector
The nitrogen levels in 4H-SiC have been determined using thermal admittance spectroscopy. The values of Ec−0.053 eV for nitrogen at the hexagonal site and Ec−0.10 eV for nitrogen at the quasicubic site agree with those reported using other techniques. The deep levels in 4H-SiC were studied using optical admittance spectroscopy. The optical admittance spectrum showed, besides the conductance peak corresponding to band to band transitions, four other conductance peaks. These peaks correspond to photoexcitation of carriers from the defect levels to the conduction band. It is inferred from a comparison with 6H-SiC that the conductance peak b4 is due to excitation of electrons from the vanadium donor at Ec−1.73 eV. The photoconductance build up transients of the Ec−1.73 eV level are described fully by one exponential term. This suggests that only one center contributed to the observed conductance. The decay kinetics of persistent photoconductance due to the Ec−1.73 eV level follow the stretched exponential form. The potential barrier against recapture of photoexcited carriers was determined to be 18 meV for the vanadium donor level in 4H-SiC.
Platinum was diffused into p+nn+ and n+pp+ silicon diodes at temperatures ranging from 860 to 910 °C for approximately 1 h. Using deep-level transient spectroscopy, six levels associated with platinum in these silicon devices were detected. Ev+0.19 eV, Ev+0.28 eV, Ev+0.33 eV, Ev+0.41 eV, Ec−0.34 eV, and Ec−0.23 eV. The concentrations, thermal emission rates, and the capture cross sections for majority carriers at these defects are reported. The Ec−0.34 eV level has not been previously characterized but is probably the dominant recombination center.
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