Effect of Z1/2, EH5, and Ci1 deep defects on the performance of n-type 4H-SiC epitaxial layers Schottky detectors: Alpha spectroscopy and deep level transient spectroscopy studies

Chaudhuri, Sandeep K.; Nguyen, Khai V.; Mandal, Krishna C.

doi:10.1063/1.4883317

Cited by 41 publications

(16 citation statements)

References 36 publications

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“…4. The DLTS measurements are consistent with our previous work 9, 16 on 50 μm n-type 4H-SiC epilayers with the exceptions of peaks 4 and 7 which involve new findings. In total, seven distinct peaks were observed in this study which corresponds to particular defect levels.…”

Section: Resultssupporting

confidence: 93%

Ru-Induced Deep Levels in Ru/4H-SiC Epilayer Schottky Diodes by Deep Level Transient Spectroscopy

Nguyen

Mandal

2015

ECS J. Solid State Sci. Technol.

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Ru-induced deep levels in 50 μm n-type 4H-SiC epitaxial layers were investigated by Deep Level Transient Spectroscopy (DLTS). Schottky diodes were fabricated by radio frequency (RF) sputtering thin layers of Ru metal on the epilayer surface and graphite paste for back Ohmic contact. Current-Voltage measurements (I-V) revealed a high barrier height of 1.70 eV and a diode ideality factor of 1.2 at room temperature (300 K). An effective carrier concentration of 4.34 × 10 14 cm −3 was determined from a Mott-Schottky plot of the Capacitance-Voltage (C-V) measurements. DLTS studies revealed seven prominent defect levels at 0.12 ± 0.02, 0.17 ± 0.01, 0.65 ± 0.01, 0.89 ± 0.03, 1.26 ± 0.04, 1.53 ± 0.06, and 1.98 ± 0.03 eV below the conduction band edge. Defect data reported in the literature suggests the new defect level of E C -(0.89 ± 0.03) eV may be correlated to Ru-induced defect formation in 4H-SiC epitaxial layer. The defect level observed at E C -(1.98 ± 0.03) eV has been observed for the first time in 50 μm 4H-SiC epilayer following Ru Schottky barrier formation and subsequent rapid thermal annealing (RTA) and this deep level has not been reported elsewhere.Silicon carbide is poised to be the high performance alternative to silicon-based devices due to its superior material properties. A wide bandgap (3.27 eV at 300 K) and large displacement energy (22-35 eV) for 4H-SiC allows devices to be operated well above room temperature and in high radiation environments without the need for bulky cryogenic cooling systems such as those used with silicon (Si) and germanium (Ge) based radiation detectors. 1 High breakdown electric field (3.0 × 10 6 V cm −1 ) and high thermal conductivity (4.9 W cm −1 K −1 ) 2 many times higher compared to Si (1.5 W cm −1 K −1 ) 2 and CdZnTe (∼9.7 × 10 −3 W cm −1 K −1 ) 3 enables high voltage operation with effective heat dissipation. Device operation in high performance applications requires the formation of metal contacts with excellent thermodynamic stability and high Schottky barriers for good current rectification. The challenge in producing consistently good Schottky contacts depends on the surface preparation of the semiconductor and how easily the contact metal diffuses into the semiconductor at the temperatures in which the device will operate.In this study, we explore the use of ruthenium (Ru) as a Schottky contact on n-type 4H-SiC epilayers and investigate defect levels induced from radio frequency (RF) sputtering and rapid thermal annealing (RTA) of the Ru Schottky contacts in the 4H-SiC epilayers. Ru is a high work function (φ Ru = 4.71 eV) rare earth transition metal with excellent physical, chemical, and electrical properties. 4 In spite of these excellent properties of Ru, there are limited literatures available on deep-level studies on Ru/4H-SiC Schottky barriers. 5-8 Experimental A 10 × 10 mm 2 sample was diced from a 4H-SiC (0001) wafer with an 8 • off-cut toward the [1120] direction highly doped with nitrogen. 50 μm epilayers were grown by hot wall chemical vapor deposition...

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Section: Resultssupporting

confidence: 93%

Ru-Induced Deep Levels in Ru/4H-SiC Epilayer Schottky Diodes by Deep Level Transient Spectroscopy

Nguyen

Mandal

2015

ECS J. Solid State Sci. Technol.

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“…Deep level capacitance transient spectroscopy is a very sensitive technique to study deep level defects in semiconducting Schottky or p-n junction devices. Figure 20 shows a DLTS spectra obtained for a 50 µm thick n-type Ni/4H-SiC (n-S50) epitaxial Schottky barrier detector in the temperature range 85-790 K [63]. Six well-resolved peaks were observed.…”

Section: Thermally Stimulated Current (Tsc) Measurementsmentioning

confidence: 99%

Advances in High-Resolution Radiation Detection Using 4H-SiC Epitaxial Layer Devices

2020

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Advances towards achieving the goal of miniature 4H-SiC based radiation detectors for harsh environment application have been studied extensively and reviewed in this article. The miniaturized devices were developed at the University of South Carolina (UofSC) on 8 × 8 mm 4H-SiC epitaxial layer wafers with an active area of ≈11 mm2. The thicknesses of the actual epitaxial layers were either 20 or 50 µm. The article reviews the investigation of defect levels in 4H-SiC epilayers and radiation detection properties of Schottky barrier devices (SBDs) fabricated in our laboratories at UofSC. Our studies led to the development of miniature SBDs with superior quality radiation detectors with highest reported energy resolution for alpha particles. The primary findings of this article shed light on defect identification in 4H-SiC epilayers and their correlation with the radiation detection properties.

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“…In a capacitance mode DLTS, the system relaxes into equilibrium by thermally emitting the trapped charges after the termination of the filling pulse resulting in capacitance transients. The thermally activated emission rate e n can be expressed as (5) where n is the carrier capture cross section, V th is the mean thermal velocity, N C is the effective density of states, g is the degeneracy of the trap level and was considered to be equal to 1 in the present calculations, and ∆E the energy separation between the trap level and the carrier band. The emission rate is related to the capacitance transient by the following relationship exp (6) where C 0 is the junction capacitance at steady-state reverse bias voltage, and ∆C is the difference in capacitance change Fig.…”

Section: B Defect Characterization By Dltsmentioning

confidence: 99%

“…Among different wide band-gap materials, silicon carbide (SiC) is a promising semiconductor due to its high thermal conductivity, breakdown electrical field, saturation electron drift velocity, and radiation resistance [1][2][3][4][5][6]. 4H-SiC polytype has the most appealing features owing to its comparatively higher band-gap, higher bulk electron mobility, and smaller anisotropy which is suitable for the fabrication of harsh environment compatible nuclear radiation detectors where conventional semiconductors (e.g., Si, Ge, CdTe, CdZnTe) show inadequate performance, though several power devices made of 4H-SiC have outperformed conventional detectors [7]- [13].…”

Section: Introductionmentioning

confidence: 99%

“…Deep level transient spectroscopy (DLTS) is a very powerful and sensitive technique for the identification of defect related parameters such as energy levels, defect concentrations, capture cross-sections, and spatial profile in semiconductors and their devices [4]- [5], [24]. A C-DLTS spectrum is generated from the temperature dependent capacitance transients followed by a saturated trap filling pulse applied to a semiconductor junction.…”

Section: Introductionmentioning

confidence: 99%

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Isochronal annealing on n-type 4H-SiC epitaxial schottky barriers and investigation of defect levels by deep level transient spectroscopy

Nguyen

Mandal

2014

2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)

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Schottky barriers were fabricated on 50 µm thick ntype 4H-SiC epitaxial layers. The effective doping concentration was calculated from high frequency (1 MHz) capacitance-voltage (C-V) measurements and was found to be ~ 9x10 14 cm -3 . Using a thermionic emission model, an effective barrier height of 1.22 eV and an ideality factor of 1.6 were calculated from the room temperature forward current-voltage (I-V) characteristics. The barrier height was also calculated from the C-V measurements and was found to be slightly higher compared to that obtained from I-V measurements, which suggests a spatial variation of surface barrier height across the device surface area. Capacitance mode deep level transient spectroscopy (DLTS) in the temperature range 80 to 800 K revealed the presence of four electron traps located in the energy range of 0.17 -1.6 eV below the conduction band edge (E c ). Three deep level defects at E c -0.67 eV (Z 1/2 ), E c -1.04 eV (EH 5 ), and E c -1.67 eV (EH 6/7 ) are detected along with one shallow level defects at E c -0.17 eV (Ti(c)). The capture cross-sections and defect densities were studied systematically through DLTS measurements before and after isochronal annealing in the temperature range of 100 -800 K. Among different defects, Z 1/2 and EH 6/7 are found to be very stable in the entire isochronal annealing range. The defects' parameters are evaluated and correlated with previous studies.Index Terms-4H-SiC, epitaxial layers, Schottky barrier, defect levels, deep level transient spectroscopy, isochronal annealing.

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Effect of Z1/2, EH5, and Ci1 deep defects on the performance of n-type 4H-SiC epitaxial layers Schottky detectors: Alpha spectroscopy and deep level transient spectroscopy studies

Cited by 41 publications

References 36 publications

Ru-Induced Deep Levels in Ru/4H-SiC Epilayer Schottky Diodes by Deep Level Transient Spectroscopy

Ru-Induced Deep Levels in Ru/4H-SiC Epilayer Schottky Diodes by Deep Level Transient Spectroscopy

Advances in High-Resolution Radiation Detection Using 4H-SiC Epitaxial Layer Devices

Isochronal annealing on n-type 4H-SiC epitaxial schottky barriers and investigation of defect levels by deep level transient spectroscopy

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