Thermal And Optical Admittance Spectroscopy Studies Of Defects In 15r-Sic

1996 ◽  
Vol 423 ◽  
Author(s):  
S. R. Smith ◽  
A. O. Evwaraye ◽  
W. C. Mitchel
Keyword(s):  
Admittance Spectroscopy ◽  
Temperature Dependent ◽  
Nitrogen Levels ◽  
Spin Resonance ◽  
Hall Effect Measurements ◽  
Heavily Doped ◽  
The Common ◽  
Spectroscopy Studies ◽  
Cv Measurements ◽  
Spectroscopy Optical

AbstractNitrogen is the common n-type dopant of the various polytypes of silicon carbide. The nitrogen levels in 4H-SiC (at EC-53 meV and EC-100 meV) and in 6H-SiC (at EC-89 meV, EC- 100 meV, and EC-125 meV) have been studied in detail by temperature dependent Hall effect measurements, electron spin resonance (ESR), and thermal admittance spectroscopy. Until now, such detailed studies of the nitrogen levels in 15R-SiC have not been carried out.Lely-grown 15R samples were used in these studies. The net carrier concentrations (ND-NA), determined by room temperature CV measurements, ranged from 1 × 1018 to 3 × 1018 cm−3. The nitrogen levels in 15R-SiC were studied using thermal admittance spectroscopy. Optical admittance spectroscopy (OAdS) was used to study the deeper defects in this polytype. It was found that optical transitions to the conduction band were inhibited in the heavily doped material.

Impurity Conduction in n-Type 4H-SIC

1996 ◽  
Vol 423 ◽  
Author(s):  
A. O. Evwaraye ◽  
S. R. Smith ◽  
W. C. Mitchel ◽  
M. D. Roth
Keyword(s):  
Activation Energies ◽  
Hopping Conduction ◽  
Admittance Spectroscopy ◽  
Temperature Dependent ◽  
Resistivity Measurements ◽  
Nitrogen Levels ◽  
Impurity Conduction ◽  
Measured Activation ◽  
Temperature Dependent Resistivity ◽  
Type Sample

AbstractImpurity conduction (or hopping conduction) has been observed in the more heavily n-type 4H-SiC samples by both temperature dependent resistivity measurements and thermal admittance spectroscopy. The measured activation energies ɛ 3 for hopping were 4–5 meV and 2.3–3.0 meV respectively. No evidence of hopping conduction was seen by either method in the sample where ND-NA < 1018 cm-3. The thermal admittance spectrum of the lightly n-type sample showed the two nitrogen levels at 53 and 100 meV.

Residual Donors in P-SiC Films

1987 ◽  
Vol 97 ◽  
Author(s):  
W. E. Carlos ◽  
W. J. Moorea ◽  
P. G. Siebenmann ◽  
J. A. Freitas ◽  
R. Kaplan ◽  
...  
Keyword(s):  
Hall Effect ◽  
Low Temperatures ◽  
Temperature Dependent ◽  
Acceptor Pair ◽  
Spin Resonance ◽  
Nitrogen Donor ◽  
Donor Acceptor ◽  
Hall Effect Measurements ◽  
Donor Acceptor Pair ◽  
Sic Films

ABSTRACTElectron Spin Resonance (ESR), temperature dependent Hall effect measurements and photoluminesence (PL) are used to examine the assumption that the residual donor in β-SiC films is nitrogen. At low temperatures the ESR has a three line isotropic spectrum which is characteristic of a central hyperfine interaction with nitrogen. The temperature dependence of the intensity of the nitrogen ESR signal correlates with the concentration of un-ionized donors measured by the Hall effect. Donor-Acceptor pair PL spectra are used to establish that the binding energy of the dominant donor in the films is the same as the nitrogen donor observed in Lely-grown samples. Neither PL nor ESR provide any evidence for the presence of a shallower donor.

Temperature-dependent screening and carrier-carrier scattering in heavily doped semiconductors

1993 ◽  
Vol 48 (23) ◽  
pp. 17121-17127 ◽  
Author(s):  
Kjeld O. Jensen ◽  
J. M. Rorison ◽  
Alison B. Walker
Keyword(s):  
Temperature Dependent ◽  
Doped Semiconductors ◽  
Carrier Scattering ◽  
Heavily Doped

Electronic Properties of Polymer-Fullerene Solar Cells

2001 ◽  
Vol 665 ◽  
Author(s):  
V. Dyakonov ◽  
I. Riedel ◽  
C. Deibel ◽  
J. Parisi ◽  
C. J. Brabec ◽  
...  
Keyword(s):  
Solar Cells ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Fill Factor ◽  
Short Circuit ◽  
Open Circuit ◽  
Light Illumination ◽  
Positive Temperature ◽  
Admittance Spectroscopy ◽  
Spin Resonance

ABSTRACTWe studied the electronic transport properties of conjugated polymer/fullerene based solar cells by means of temperature and illumination intensity dependent current-voltage characteristics, admittance spectroscopy and light-induced electron spin resonance. The short-circuit current density increases with temperature at all light illumination intensities applied, i.e., from 100 mW/cm2 to 0.1 mW/cm2 (white light), whereas a temperature independent behavior was expected. An increase of the open-circuit voltage from 850 mV to 940 mV was observed, when cooling down the device from room temperature to 100 K. The fill factor depends strongly on temperature with a positive temperature coefficient in the whole temperature range. In contrast, the light intensity dependence of the fill factor shows a maximum of 52% at intermediate illumination intensities (3 mW/cm2) and decreases subsequently, when increasing the intensity up to 100 mW/cm2. Further studies by admittance spectroscopy revealed two frequency dependent contributions to the device capacitance. One, as we believe, originates from trapping states located at the interface between composite and metal electrode with an activation energy of EA=180 meV, and the other one is from very shallow bulk states with EA=10 meV. The origin of the latter is possibly the thermally activated conductivity. The photo-generation of charge carriers and their fate in these blends have been studied by light-induced electron spin resonance. We can clearly distinguish between photo-generated electrons and holes in the composites due to different spectroscopic splitting factors (g-factors). Additional information on the environmental axial symmetry of the holes located on the polymer chains as well as on a lower, rhombic, symmetry of the electrons located on the methanofullerene molecules has been obtained. The origin of the signals and parameters of the g-tensor have been confirmed from studies on a hole doped polymer.

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