Characterization of deep level defects in sublimation grown p-type 6H-SiC epilayers by deep level transient spectroscopy (original) (raw)
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Physica B: Condensed Matter, 2012
Deep level transient spectroscopy (DLTS) is employed to study deep level defects in n-6H-SiC (silicon carbide) epilayers grown by the sublimation method. To study the deep level defects in n-6H-SiC, we used as-grown, nitrogen doped and nitrogen-boron co-doped samples represented as ELS-1, ELS-11 and ELS-131 having net (N D -N A ) $ 2.0 Â 10 12 cm À 3 , 2 Â 10 16 cm À 3 and 9 Â 10 15 cm 3 , respectively. The DLTS measurements performed on ELS-1 and ELS-11 samples revealed three electron trap defects (A, B and C) having activation energies E c -0.39 eV, E c -0.67 eV and E c -0.91 eV, respectively. While DLTS spectra due to sample ELS-131 displayed only A level. This observation indicates that levels B and C in ELS-131 are compensated by boron and/or nitrogen-boron complex. A comparison with the published data revealed A, B and C to be E 1 /E 2 , Z 1 /Z 2 and R levels, respectively.
High-Temperature Deep Level Transient Spectroscopy on As-Grown P-Type 4H-SiC Epilayers
Japanese Journal of Applied Physics, 2006
Deep levels in as-grown p-type 4H-SiC have been investigated. Three hole traps, namely HK2, HK3, and HK4, were detected by deep level transient spectroscopy (DLTS) in the temperature range from 350 to 700 K. The concentration of each trap is approximately 1{ 3 Â 10 12 cm À3. Activation energy is estimated to be E V þ 0:84 eV for HK2, E V þ 1:27 eV for HK3, and E V þ 1:44 eV for HK4. These hole traps may be donor-like (þ=0) traps according to the double-correlated DLTS measurements. The concentrations of HK3 and HK4 decrease below the detection limit (1 Â 10 11 cm À3) by annealing at 1350 C. On the other hand, the HK2 center is thermally more stable, the annealing temperature being approximately 1550 C.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate the effect of alpha-particle irradiation on the electrical properties of nitrogen-doped 4H-SiC. The samples were bombarded with alpha-particles at room temperature (300 K) using an americium-241 (241 Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E 0.09 , E 0.11 , E 0.16 and E 0.65. After irradiation with a fluence of 4.1 × 10 10 alpha-particles-cm-2 , DLTS measurements indicated the presence of two new deep levels, E 0.39 and E 0.62 with energy level, E C-0.39 eV and E C-0.62 eV, with an apparent capture cross sections of 2×10-16 and 2×10-14 cm 2 , respectively. Furthermore, irradiation with fluence of 8.9×10 10 alpha-particles-cm-2 resulted in disappearance of shallow defects due to a lowering of the Fermi level. These defectsminutes. Defects, E 0.39 and E 0.42 with close emission rates were attributed to silicon or carbon vacancy and could only be separated by using high resolution Laplace-DLTS. The DLTS peaks at E C-(0.55-0.70) eV (known as Z 1 /Z 2) were attributed to an isolated carbon vacancy (V C).
Deep level transient spectroscopy study of defects in hydrogen implanted p-type 4H-SiC
Journal of Applied Physics, 2007
p-type 4H-SiC epitaxial layers grown by chemical vapor deposition have been implanted with 200 and 100 keV protons at five different implantation temperatures. An isochronal annealing series was performed from 100 to 1800°C, and Al-doped epitaxial layers have been characterized by means of deep level transient spectroscopy ͑DLTS͒ after each annealing step. DLTS measurements were carried out in the 150-670 K temperature range and revealed the presence of eight hole traps located in the 0.18-1.8 eV range above the valence band ͑E V ͒. Heat treatments for temperatures above 700°C showed the progressive reactivation of the Al doping in the implanted region, which is completed after a 1500°C annealing treatment. Two traps located at E V + 0.44 eV and E V + 1.8 eV are persistent even after annealing at 1800°C, while the other traps anneal out after heat treatments at ഛ1700°C. An activation energy for dissociation of 6.2 eV is estimated for the hole trap at E V + 0.79 eV, and the nature of this defect is discussed on the basis of previous experimental results and theoretical calculations. Furthermore, the study of the annealing behavior as a function of the implantation temperature shows that the detected traps display an increase of concentration for increasing implantation temperatures.
Deep levels in iron doped n- and p-type 4H-SiC
Journal of Applied Physics, 2011
Deep levels were detected in Fe-doped n-and p-type 4H-SiC using deep level transient spectroscopy (DLTS). One defect level (E C -0.39 eV) was detected in n-type material. DLTS spectra of p-type 4H-SiC show two dominant peaks (E V þ 0.97 eV and E V þ 1.46 eV). Secondary ion mass spectrometry measurements confirm the presence of Fe in both n-and p-type 4H-SiC epitaxial layers. The majority of the capture process for Fe1, Fe2, and Fe3 is multi-phonon emission assisted. These three detected peaks are suggested to be related to Fe.
Low-doped 6H-SiC n-type epilayers grown by sublimation epitaxy
Materials Science and Engineering: B, 2000
Sublimation epitaxy has not yet been a technique of prime importance to grow epitaxial 6H-SiC layers because grown layers have always shown a residual net doping level higher than 10 16 cm − 3 and a high compensation level. We present here results obtained with an optimized technology of sublimation epitaxial growth, which can be used to obtain structurally perfect layers with a concentration of uncompensated donors as low as 10 15 cm − 3 . These layers have been both physically and electrically characterized. Deep level transient spectroscopy indicates that the concentration of deep levels is greatly reduced. As a consequence the hole diffusion length is significantly increased up to about 2.5 mm, as confirmed by electron beam induced current measurements. So these optimized layers are envisaged for the fabrication of high voltage diodes or bipolar transistors.
Journal of Applied Physics, 2007
The effect of the Schottky barrier height on the detection of the concentration of midgap defects using deep level transient spectroscopy ͑DLTS͒ is experimentally and theoretically studied for EH 6 and EH 7 defects in 4H-SiC. In this special case, the DLTS signal height for EH 6 and EH 7 increases with increasing barrier height and saturates at values above 1.5 and 1.7 eV, respectively. Below 1.1 eV, the DLTS peak completely disappears for both defects. The experimental data are explained by a theoretical model. The course of the quasi-Fermi level in the space charge region is calculated as a function of the reverse current through it, which is determined by the barrier height, and the reverse bias applied.
Surface & Coatings Technology, 2018
We have characterised the deep level defects present before and after annealing the proton-irradiated Ni/nitrogen-doped 4H-SiC Schottky barrier diodes (SBDs) using deep level transient spectroscopy. The bombardment of the sample was carried out at a fluence of 1.0 × 10 12 cm −2. The quality of the Ni/4H-SiC SBDs was evaluated before and after proton irradiation and annealing by current-voltage (I-V) and capacitance-voltage (C-V) measurements, carried out at room temperature (300 K). The I-V and C-V results revealed extensive degradation of the diodes properties after proton irradiation at the aforementioned fluence. Rectification properties of the Ni/ 4H-SiC SBDs recovered gradually after annealing in flowing argon at temperatures varying from 125 to 625°C. The presence of four electron traps (E c-0.10, E c-0.13, E c-0.18 and E c-0.69 eV) was observed in as-grown Ni/ 4H-SiC SBDs. Deep level defects, E c-0.42 and E c-0.76 eV, were revealed after annealing the proton-irradiated SBDs up to 225°C. The two defects observed at 225°C later annealed out at 425°C, causing a significant change in the spectrum. The annealing out of E c-0.42 and E c-0.76 eV at 425°C was concurrent with detection of two electron traps, E c-0.31 and E c-0.62 eV. We speculate that the defects E c-0.42 and E c-0.76 eV have a link or relationship with defects E c-0.31 and E c-0.62 eV, respectively. The defect, E c-0.31 eV, was stable up to hightemperature annealing and was attributed to a carbon interstitial.
Journal of Applied Physics, 2010
Intentionally doped n-type 4H-SiC films were grown on 4°and 8°off-axis substrates to investigate the influence of electron concentration on the incorporation of electron traps Z 1/2 and EH 6/7. No discernible change was seen in the Z 1/2 and EH 6/7 trap concentrations for films grown on both orientations with electron concentrations in the range of 1 ϫ 10 14 to 1 ϫ 10 16 cm −3 , suggesting that the Z 1/2 and EH 6/7 traps are not associated with isolated carbon vacancies. The defect concentrations did not correlate with the measured carrier lifetimes, which is consistent with a carrier lifetime controlled by other recombination centers. Observed decreases in lifetime were related to increases in doping levels, with similar trends seen for both orientations. Carrier lifetimes in 8°material were slightly longer than in 4°films for similar doping concentrations, most likely being associated with surface recombination and/or extended defects.
Journal of Applied Physics, 2012
We have investigated deep level centers in n-type and semi-insulating (SI) 4H-SiC epitaxial layers by thermally stimulated current (TSC) spectroscopy. The epitaxial layers were grown using chemical vapor deposition utilizing a dichlorosilane precursor. Both epitaxial layers exhibited relatively shallow levels related to Al, B, L- and D-centers. A deep level center with an activation energy of 1.1 eV, peaked at ∼400 K, was detected in the n-type epitaxial layer and correlated with the IL2 level and the 1.1 eV center in a high purity bulk SI 4H-SiC. The TSC spectra of the SI epitaxial layer was dominated by the peaks at 525–585 K that we attributed to intrinsic defects and their complexes with energy levels close to the middle of the bandgap. The TSC spectra of SI epitaxial layer exhibited peaks with different current polarity which is explained by thermoelectric effect and the built-in electric field reversal. The results of the transfer length method measurements of the SI epitaxial...