Charged and neutral defect states in a-Si:H determined from improved analysis of the constant photocurrent method

AbstractCPM and PDS spectra of a-Si:H yield identical shape of the Urbach tail, while the defect absorption measured by PDS differs significantly from CPM. In this work an analysis of CPM and PDS spectra of annealed and degraded films is presented. Numerical simulations of CPM and PDS data, taking into account optical transitions, capture and emission processes as well as the Fermi level, yield information on the energy distribution and the charge state of the defects. The simulations reveal the coexistence of defects in the D−, D+ and D0 states. The defect distribution is dominated by charged states as predicted by the defect-pool model. Good agreement between measured and simulated PDS and CPM spectra can be obtained in the case of a homogeneous defect density. It is shown that differences between CPM and PDS are due to different sensitivities of the techniques to charged and neutral defect states. Microscopic inhomogeneities may cause significant additional differences.

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Charged Defect State Distributions Obtained from the Analysis of Photoconductivities in Intrinsic a-Si:H Films

MRS Proceedings ◽

10.1557/proc-336-413 ◽

1994 ◽

Vol 336 ◽

Cited By ~ 6

Author(s):

Mehmet Güneş ◽

R. W. Collins ◽

C. R. Wronski

Keyword(s):

Charged Defect ◽

Defect States ◽

State Distribution ◽

Spin Resonance ◽

Neutral Defect ◽

Gap States ◽

Hydrogenated Amorphous ◽

Defect Densities ◽

Positively Charged ◽

Spin Densities

ABSTRACTSteady-state photoconductivity, sub-bandgap absorption and electron spin resonance (ESR) Measurements were carried out on annealed and light soaked intrinsic hydrogenated Amorphous silicon (a-Si:H) films. The experimental results were modeled using detailed numerical Model. The defect densities derived from the sub-bandgap absorption in the light soaked films were correlated with the ESR spin densities. Selfconsistent fitting of the data was obtained using a gap state distribution which consists of positively charged defect states above, negatively charged defect states below and neutral defect states at about Midgap. Both the annealed and the light degraded states are modeled using the same distribution of gap states whose densities increase upon light soaking with a slight increase in the ratio of the neutral to charged defect densities. These results on intrinsic a-Si:H are consistent with those of charged defect Models.

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Charged and neutral defect states in a-Si:H determined from improved analysis of the constant photocurrent method

Solar Energy Materials and Solar Cells ◽

10.1016/0927-0248(95)00140-9 ◽

1996 ◽

Vol 41-42 ◽

pp. 529-536 ◽

Cited By ~ 2

Author(s):

F SIEBKE ◽

H STIEBIG ◽

A ABOARAIS ◽

H WAGNER

Keyword(s):

Defect States ◽

Neutral Defect

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Defect Distributions in Doped and Undoped A-SiGe:H Alloys

MRS Proceedings ◽

10.1557/proc-507-403 ◽

1998 ◽

Vol 507 ◽

Cited By ~ 2

Author(s):

Helmut Stiebig ◽

Frank Siebke ◽

Reinhard Carius ◽

Josef Klomfaβ

Keyword(s):

Absorption Spectra ◽

Defect Density ◽

Charged Defect ◽

Defect States ◽

Charge Neutrality ◽

Photothermal Deflection Spectroscopy ◽

Neutral Defect ◽

Related Defect ◽

Gap States ◽

Good Agreement

ABSTRACTIn this work, gap states in doped and undoped a-SiGe:H alloys are examined by numerical simulations of sub-bandgap absorption spectra measured by the constant photocurrent method and photothermal deflection spectroscopy. Deconvolution methods, neglecting the condition of charge neutrality, can be used for a rough estimate of the defect density value but not for ob- taining detailed information on the distribution of gap states in undoped samples. Our numerical analysis uses adapted occupation statistics and takes into account the condition of charge neutrality. Good agreement between measured and simulated PDS and CPM spectra is obtained. For a certain composition, i.e. a certain bandgap, the investigation of doped films yields infor- mation on the density and the position of charged defect states in the bandgap. In addition, the density of neutral defect states can be derived from a comparison of CPM and PDS spectra. The results reveal the coexistence of charged and neutral defects. In doped as well as in undoped films, charged defect states dominate the defect density. In the investigated range of compo- sitions the defect distribution of a-SiGe:H is similar to those found in a-Si:H. The width of the defect distributions does not decrease with decreasing bandgap. No evidence for a different be- havior of Si- and Ge-related defect states can be found in sub-bandgap absorption spectra.

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Spectrum of Defect States in Porous Organic Low-k Dielectric Films, Annealed in Argon and Nitrogen

MRS Proceedings ◽

10.1557/proc-766-e8.5 ◽

2003 ◽

Vol 766 ◽

Author(s):

V. Ligatchev ◽

T.K.S. Wong ◽

T.K. Goh ◽

Rusli Suzhu Yu

Keyword(s):

Deep Level ◽

Dielectric Films ◽

Silicon Substrates ◽

Reverse Bias Voltage ◽

Defect States ◽

Single Side ◽

Sandwich Type ◽

Transient Spectroscopy ◽

P Type ◽

Spectrum Deconvolution

AbstractDefect spectrum N(E) of porous organic dielectric (POD) films is studied with capacitance deep-level-transient-spectroscopy (C-DLTS) in the energy range up to 0.7 eV below conduction band bottom Ec. The POD films were prepared by spin coating onto 200mm p-type (1 – 10 Δcm) single-side polished silicon substrates followed by baking at 325°C on a hot plate and curing at 425°C in furnace. The film thickness is in the 5000 – 6000 Å range. The ‘sandwich’ -type NiCr/POD/p-Si/NiCr test structures showed both rectifying DC current-voltage characteristics and linear 1/C2 vs. DC reverse bias voltage. These confirm the applicability of the C-DLTS technique for defect spectrum deconvolution and the n-type conductivity of the studied films. Isochronal annealing (30 min in argon or 60 min in nitrogen) has been performed over the temperature range 300°C - 650°C. The N(E) distribution is only slightly affected by annealing in argon. However, the distribution depends strongly on the annealing temperature in nitrogen ambient. A strong N(E) peak at Ec – E = 0.55 – 0.60 eV is detected in all samples annealed in argon but this peak is practically absent in samples annealed in nitrogen at Ta < 480°C. On the other hand, two new peaks at Ec – E = 0.12 and 0.20 eV appear in the N(E) spectrum of the samples annealed in nitrogen at Ta = 650°C. The different features of the defect spectrum are attributed to different interactions of argon and nitrogen with dangling carbon bonds on the intra-pore surfaces.

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EPR spectra and defect states in glasses of the GexS100-x system

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19821787 ◽

1982 ◽

Vol 47 (7) ◽

pp. 1787-1793 ◽

Cited By ~ 3

Author(s):

Miloslav Frumar ◽

Gustáv Plesch ◽

Eva Černošková ◽

Václav Černý ◽

Ladislav Tichý ◽

...

Keyword(s):

Experimental Data ◽

Epr Spectra ◽

Defect States ◽

Composition Region ◽

Active Defect ◽

Temperature Conditions ◽

Defect Centres

Glasses of the GexS100-x system were studied in the region of 30 ⪬ x ⪬ 45. The concept of magnetically active defect centres was employed to account for the EPR spectra of pure samples as well as those doped with silver or iodine, prepared in different temperature conditions. In terms of this concept a consistent interpretation of the experimental data could be given for the composition region applied.

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The Instability Characteristics of Amorphous Silicon Thin Film Transistors with Various Interfacial and Bulk Defect States

Japanese Journal of Applied Physics ◽

10.1143/jjap.36.6226 ◽

1997 ◽

Vol 36 (Part 1, No. 10) ◽

pp. 6226-6229 ◽

Cited By ~ 1

Author(s):

Huang-Chung Cheng ◽

Jun-Wei Tsai ◽

Chun-Yao Huang ◽

Fang-Chen Luo ◽

Hsing-Chien Tuan

Keyword(s):

Thin Film ◽

Amorphous Silicon ◽

Thin Film Transistors ◽

Defect States ◽

Silicon Thin Film

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Correlation between Defects and Electrical Performances of Ion-Irradiated 4H-SiC p–n Junctions

Materials ◽

10.3390/ma14081966 ◽

2021 ◽

Vol 14 (8) ◽

pp. 1966

Author(s):

Domenico Pellegrino ◽

Lucia Calcagno ◽

Massimo Zimbone ◽

Salvatore Di Franco ◽

Antonella Sciuto

Keyword(s):

Deep Level ◽

Electrical Characterization ◽

High Fluence ◽

Defect States ◽

Exponential Parameter ◽

Current Voltage ◽

Different Temperatures ◽

In Series ◽

Transient Spectroscopy ◽

Fluence Range

In this study, 4H-SiC p–n junctions were irradiated with 700 keV He+ ions in the fluence range 1.0 × 1012 to 1.0 × 1015 ions/cm2. The effects of irradiation were investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements, while deep-level transient spectroscopy (DLTS) was used to study the traps introduced by irradiation defects. Modifications of the device’s electrical performances were observed after irradiation, and two fluence regimes were identified. In the low fluence range (≤1013 ions/cm2), I–V characteristics evidenced an increase in series resistance, which can be associated with the decrease in the dopant concentration, as also denoted by C–V measurements. In addition, the pre-exponential parameter of junction generation current increased with fluence due to the increase in point defect concentration. The main produced defect states were the Z1/2, RD1/2, and EH6/7 centers, whose concentrations increased with fluence. At high fluence (>1013 ions/cm2), I–V curves showed a strong decrease in the generation current, while DLTS evidenced a rearrangement of defects. The detailed electrical characterization of the p–n junction performed at different temperatures highlights the existence of conduction paths with peculiar electrical properties introduced by high fluence irradiation. The results suggest the formation of localized highly resistive regions (realized by agglomeration of point defects) in parallel with the main junction.

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