Papers by Keyword: EH_6/7

Abstract: We employed Laplace transform deep level transient spectroscopy (LDLTS) for the resolution of the EH6/7 center in n-type 4H-SiC epilayers. Our results suggest that this technique is effective in separating the emission rates of the EH6 and EH7 levels. From the Arrhenius dependence of the emission rates we could estimate the energy position of EH6 and EH7 as 1.39 and 1.49 eV below the minimum of the conduction band edge, respectively. Generation of of EH6 and EH7 centers by low-energy electron irradiation (dose dependence) was also investigated. At last, a double pulse Laplace DLTS is performed in order to show the electric filed dependence of the emission rates of EH6 and EH7.

Abstract: In this paper the impact of high temperature annealing on the formation of intrinsic defects in 4H-SiC such as Z_1/2 and EH_6/7 was examined. Therefore, three epitaxial layers with various initial concentrations of the Z_1/2- and EH_6/7-centers (10¹¹ – 10¹³ cm^-3) were investigated. It turns out that depending on the initial defect concentration the high temperature annealing leads to a monotone increase of the Z_1/2- and EH_6/7-concentration in a temperature range from 1600 to 1750°C. For a defined temperature above these values, the resulting defect concentration is independent of the sample’s initial values. Beside the growth conditions themselves such as C/Si ratio the thermal post-growth processing has a severe impact on the carrier lifetime which must be taken into account during device fabrication.

Abstract: Deep Level Transient Spectroscopy (DLTS) and Double-correlated DLTS (DDLTS) measurements have been conducted on Schottky contacts fabricated on n-type 4H-SiC epilayers using different contact metals in order to separate the EH₆- and EH₇-centers, which usually appear as a broad double peak in DLTS spectra. The activation energy of EH₆ (E_C - E_T(EH₆) = 1.203 eV) turns out to be independent of the electric field. As a consequence, EH₆ is acceptor-like according to the missing Poole-Frenkel effect. Therefore, it can be excluded that the EH₆-center and the prominent acceptor-like Z_1/2-center belong to different charge states of the same microscopic defect as theoretically suggested. It is proposed that EH₆ is a complex containing a carbon vacancy and another component available at high concentrations. The activation energy of EH₇ (E_C - E_T(EH₇) = 1.58 eV) has been evaluated indirectly by fitting the DLTS spectra of the EH_6/7 double peak taking the previously determined parameters of EH₆ into account.

Abstract: Annealing of the Z1/2 and EH6/7 has been studied by DLTS after ion implantation of MeV Si ions and subsequent annealing in either N2 or O2 at 1150 °C, in the dose range 1 - 4 × 108 Si / cm2. It is found that the annealing rate of these prominent defects is greatly enhanced after thermal oxidation, and in particular close to the surface area, due to injection of a defect species which annihilates with both Z1/2 and EH6/7. The migration part of the diffusion coefficient of the injected defect is established to be in the range 1 – 2 × 10-8 cm2/s, and the measured concentration versus depth profiles of both Z1/2 and EH6/7 are accurately simulated by a simple model.