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1994 Fiscal Year Final Research Report Summary

Characterization of Sturctural Disorder by means of Polarized Photoreflectance in Amorphous Semiconductors

Research Project

Project/Area Number 05650305
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Electronic materials/Electric materials
Research InstitutionOsaka University

Principal Investigator

OKAMOTO Hiroaki  Osaka University, Faculty of Engineering Science, Associate Professor, 基礎工学部, 助教授 (90144443)

Co-Investigator(Kenkyū-buntansha) HATTORI Kiminori  Osaka University, Faculty of Engineering Science, Research Associate, 基礎工学部, 助手 (80228486)
Project Period (FY) 1993 – 1994
KeywordsAmorphous semiconductor / Structural disorder / Photoreflectance / Polarized electroabsorption / Band edge states / Carrier mobility
Research Abstract

Polarized Electroabsorption technique (PEA) has been developed for the determination of carrier mean free path as well as mobility near the band edge in amorphous semiconductors. The method is based upon the result of microscopic theory of optical spectrum in the presence of external electric fields, which indicates that an "extrinsic" polarization dependence of the EA signal appears due to the fieldinduced change in the matrix element for transitions involving localized states, so that it serves as a measure of the degree of disorder in amorphous semiconductors. Measured EA signal intensity ratio between field-light polarization parallel and perpendicular conditions is transrated into carrier mean free path and band edge mobility. We have applied this new technique to amorphous silicon alloys. The conclusions reached from the present work are as follows ;
1) The electron (hole) mean free path is about 12* (5*) for device quality undoped a-Si : H,which yields estimate of the electron (hole) mobility of 10 cm2/Vs (3cm2/Vs).
2) The mobilities attain maxima at a particular deposition temperature which would depend on details of deposition conditions.
3) Annealing treatment on a-Si : H deposited at a low temperature improves carrier mobilities through the relaxation of structural disorder.
4) Alloying with carbon leads to a continuous reduction of mobility, with the largest drop (15%) for a carbon concentration of about 10 at%, this being in sharp contrast to a less-pronounced effect by germanium alloying.
5) Phosphorus doping ramarkably detoriorates the electron mobility, while the hole mobility remains almost unchanged from that in undoped material.

  • Research Products

    (6 results)

All Other

All Publications (6 results)

  • [Publications] 堤 保雄: "Polavized electroabsorption in hydrogenated awurphous silicon alloys and its implication for band edge parameters" Philos Mag.B69. 253-261 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 岡本 博明: "Hall effect near the mobility edge" J.Non-Cryst.Solids. 164-166. 445-448 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 堤 保雄: "Polavized electroabsorption and carrier mobilities in awouphous silicon alloys" Mat.Res.Soc.Symp.Proc.336. 343-351 (1994)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Y.Tsutsumi: ""Polarized Electroabsorption Effect in Hydrogenated Amorphous Silicon Alloys and Its Implication for Band Edge Parameters"" Philos.Mag. B69. 253-261 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] H.Okamoto: ""Hall Effect near the Mobility Edge"" J.Non-Cryst.Solids. 164&166. 445-448 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Y.Tsutsumi: ""Polarized Electroabsorption and Carrier Mobilities in Amorphous Silicon Alloys"" Mat.Res.Soc.Symp.Proc.336. 343-351 (1994)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1996-04-15  

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