skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

Abstract

The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparing intrinsic amorphous and microcrystalline silicon, it is found that the relationship between defect density and photoconductivity is different in both undoped materials, while a similar strong influence of the position of the Fermi level on photoconductivity via the charge carrier lifetime is found in the doped materials. The latter allows a quantitative determination of the value of the transport gap energy in microcrystalline silicon. The photoconductivity in intrinsic microcrystalline silicon is, on one hand, considerably less affected by the bombardment but, on the other hand, does not generally recover with annealing of the defects and is independent from the spin density which itself can be annealed back to the as-deposited level. For amorphous silicon and material prepared close to the crystalline growth regime, the results for nonequilibrium transport fit perfectly to a recombination model basedmore » on direct capture into neutral dangling bonds over a wide range of defect densities. For the heterogeneous microcrystalline silicon, this model fails completely. The application of photoconductivity spectroscopy in the constant photocurrent mode (CPM) is explored for the entire structure composition range over a wide variation in defect densities. For amorphous silicon previously reported linear correlation between the spin density and the subgap absorption is confirmed for defect densities below 10{sup 18} cm{sup -3}. Beyond this defect level, a sublinear relation is found i.e., not all spin-detected defects are also visible in the CPM spectra. Finally, the evaluation of CPM spectra in defect-rich microcrystalline silicon shows complete absence of any correlation between spin-detected defects and subband gap absorption determined from CPM: a result which casts considerable doubt on the usefulness of this technique for the determination of defect densities in microcrystalline silicon. The result can be related to the inhomogeneous structure of microcrystalline silicon with its consequences on transport and recombination processes.« less

Authors:
; ; ; ; ;  [1]
  1. Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich, Germany and National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov (Ukraine)
Publication Date:
OSTI Identifier:
21192549
Resource Type:
Journal Article
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 79; Journal Issue: 10; Other Information: DOI: 10.1103/PhysRevB.79.104205; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1098-0121
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; ANNEALING; CARRIER LIFETIME; CHARGE CARRIERS; CORRELATIONS; CRYSTAL DEFECTS; CRYSTAL GROWTH; DENSITY; DOPED MATERIALS; ELECTRON BEAMS; ELECTRON SPIN RESONANCE; ENERGY GAP; FERMI LEVEL; PERT METHOD; PHOSPHORUS; PHOTOCONDUCTIVITY; RECOMBINATION; SEMICONDUCTOR MATERIALS; SILICON; SPECTRA; SPECTROSCOPY; SPIN; THIN FILMS

Citation Formats

Astakhov, Oleksandr, Carius, Reinhard, Finger, Friedhelm, Petrusenko, Yuri, Borysenko, Valery, Barankov, Dmytro, Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich, and National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov. Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon. United States: N. p., 2009. Web. doi:10.1103/PHYSREVB.79.104205.
Astakhov, Oleksandr, Carius, Reinhard, Finger, Friedhelm, Petrusenko, Yuri, Borysenko, Valery, Barankov, Dmytro, Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich, & National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov. Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon. United States. doi:10.1103/PHYSREVB.79.104205.
Astakhov, Oleksandr, Carius, Reinhard, Finger, Friedhelm, Petrusenko, Yuri, Borysenko, Valery, Barankov, Dmytro, Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich, and National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov. Sun . "Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon". United States. doi:10.1103/PHYSREVB.79.104205.
@article{osti_21192549,
title = {Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon},
author = {Astakhov, Oleksandr and Carius, Reinhard and Finger, Friedhelm and Petrusenko, Yuri and Borysenko, Valery and Barankov, Dmytro and Forschungszentrum Juelich, Institute of Energy Research-Photovoltaic, 52425 Juelich and National Science Center-Kharkov Institute of Physics and Technology, Cyclotron Science and Research Establishment, 61108 Kharkov},
abstractNote = {The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparing intrinsic amorphous and microcrystalline silicon, it is found that the relationship between defect density and photoconductivity is different in both undoped materials, while a similar strong influence of the position of the Fermi level on photoconductivity via the charge carrier lifetime is found in the doped materials. The latter allows a quantitative determination of the value of the transport gap energy in microcrystalline silicon. The photoconductivity in intrinsic microcrystalline silicon is, on one hand, considerably less affected by the bombardment but, on the other hand, does not generally recover with annealing of the defects and is independent from the spin density which itself can be annealed back to the as-deposited level. For amorphous silicon and material prepared close to the crystalline growth regime, the results for nonequilibrium transport fit perfectly to a recombination model based on direct capture into neutral dangling bonds over a wide range of defect densities. For the heterogeneous microcrystalline silicon, this model fails completely. The application of photoconductivity spectroscopy in the constant photocurrent mode (CPM) is explored for the entire structure composition range over a wide variation in defect densities. For amorphous silicon previously reported linear correlation between the spin density and the subgap absorption is confirmed for defect densities below 10{sup 18} cm{sup -3}. Beyond this defect level, a sublinear relation is found i.e., not all spin-detected defects are also visible in the CPM spectra. Finally, the evaluation of CPM spectra in defect-rich microcrystalline silicon shows complete absence of any correlation between spin-detected defects and subband gap absorption determined from CPM: a result which casts considerable doubt on the usefulness of this technique for the determination of defect densities in microcrystalline silicon. The result can be related to the inhomogeneous structure of microcrystalline silicon with its consequences on transport and recombination processes.},
doi = {10.1103/PHYSREVB.79.104205},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
issn = {1098-0121},
number = 10,
volume = 79,
place = {United States},
year = {2009},
month = {3}
}