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Title: Impact ionization of excitons in Ge/Si structures with Ge quantum dots grown on the oxidized Si(100) surfaces

Photoconductivity (PC) of Si/Ge structures with Ge quantum dots (QDs) grown on the Si(100) surfaces covered with the ultrathin, about 0.3–0.5 nm thick, SiO{sub 2} films is studied as a function of the interband light intensity under various lateral voltages. The structures exhibit PC with steps and a step with a peak at the step edge for low- and high-temperature grown structures, respectively. These PC features are associated with the impact ionization of QD-related excitons. The PC at step edges increases by several orders of magnitude for a certain value which is governed by the balance between rates of photo-generation, recombination, and impact ionization of excitons. The electron localization deeper in Si from the Ge QD layer in conjunction with a narrow binding-energy distribution of excitons is suggested to be the main reason that provides the sharpness of PC steps. The PC appears to be very sensitive to the impact ionization and QD preparation conditions. This allows revealing the specific characteristics of QD structures, related to their electronic and structural properties.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4]
  1. A. V. Rzhanov Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation)
  2. (Russian Federation)
  3. Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)
  4. Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan)
Publication Date:
OSTI Identifier:
22304386
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BINDING ENERGY; DISTRIBUTION; EXCITONS; GERMANIUM; IONIZATION; LAYERS; PHOTOCONDUCTIVITY; QUANTUM DOTS; RECOMBINATION; SILICON; SILICON OXIDES; SURFACES; THIN FILMS; VISIBLE RADIATION