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Title: Optical properties of p–i–n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing

Abstract

Silicon nanocrystals are formed in the i layers of p–i–n structures based on a-Si:H using pulsed laser annealing. An excimer XeCl laser with a wavelength of 308 nm and a pulse duration of 15 ns is used. The laser fluence is varied from 100 (below the melting threshold) to 250 mJ/cm{sup 2} (above the threshold). The nanocrystal sizes are estimated by analyzing Raman spectra using the phonon confinement model. The average is from 2.5 to 3.5 nm, depending on the laser-annealing parameters. Current–voltage measurements show that the fabricated p–i–n structures possess diode characteristics. An electroluminescence signal in the infrared (IR) range is detected for the p–i–n structures with Si nanocrystals; the peak position (0.9–1 eV) varies with the laser-annealing parameters. Radiative transitions are presumably related to the nanocrystal–amorphous-matrix interface states. The proposed approach can be used to produce light-emitting diodes on non-refractory substrates.

Authors:
; ; ;  [1]; ;  [2];  [3]; ;  [2]
  1. Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
  2. Institute of Physics ASCR (Czech Republic)
  3. Institute of Chemical Process Fundamentals of the ASCR (Czech Republic)
Publication Date:
OSTI Identifier:
22649738
Resource Type:
Journal Article
Resource Relation:
Journal Name: Semiconductors; Journal Volume: 50; Journal Issue: 7; Other Information: Copyright (c) 2016 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMORPHOUS STATE; ANNEALING; ELECTROLUMINESCENCE; HYDROGENATION; INTERFACES; IRRADIATION; LASER RADIATION; LAYERS; LIGHT EMITTING DIODES; MATRIX MATERIALS; NANOSTRUCTURES; OPTICAL PROPERTIES; PHONONS; RAMAN SPECTRA; SEMICONDUCTOR JUNCTIONS; SILICON; SUBSTRATES

Citation Formats

Krivyakin, G. K., Volodin, V. A., E-mail: volodin@isp.nsc.ru, Kochubei, S. A., Kamaev, G. N., Purkrt, A., Remes, Z., Fajgar, R., Stuchliková, T. H., and Stuchlik, J.. Optical properties of p–i–n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing. United States: N. p., 2016. Web. doi:10.1134/S1063782616070101.
Krivyakin, G. K., Volodin, V. A., E-mail: volodin@isp.nsc.ru, Kochubei, S. A., Kamaev, G. N., Purkrt, A., Remes, Z., Fajgar, R., Stuchliková, T. H., & Stuchlik, J.. Optical properties of p–i–n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing. United States. doi:10.1134/S1063782616070101.
Krivyakin, G. K., Volodin, V. A., E-mail: volodin@isp.nsc.ru, Kochubei, S. A., Kamaev, G. N., Purkrt, A., Remes, Z., Fajgar, R., Stuchliková, T. H., and Stuchlik, J.. Fri . "Optical properties of p–i–n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing". United States. doi:10.1134/S1063782616070101.
@article{osti_22649738,
title = {Optical properties of p–i–n structures based on amorphous hydrogenated silicon with silicon nanocrystals formed via nanosecond laser annealing},
author = {Krivyakin, G. K. and Volodin, V. A., E-mail: volodin@isp.nsc.ru and Kochubei, S. A. and Kamaev, G. N. and Purkrt, A. and Remes, Z. and Fajgar, R. and Stuchliková, T. H. and Stuchlik, J.},
abstractNote = {Silicon nanocrystals are formed in the i layers of p–i–n structures based on a-Si:H using pulsed laser annealing. An excimer XeCl laser with a wavelength of 308 nm and a pulse duration of 15 ns is used. The laser fluence is varied from 100 (below the melting threshold) to 250 mJ/cm{sup 2} (above the threshold). The nanocrystal sizes are estimated by analyzing Raman spectra using the phonon confinement model. The average is from 2.5 to 3.5 nm, depending on the laser-annealing parameters. Current–voltage measurements show that the fabricated p–i–n structures possess diode characteristics. An electroluminescence signal in the infrared (IR) range is detected for the p–i–n structures with Si nanocrystals; the peak position (0.9–1 eV) varies with the laser-annealing parameters. Radiative transitions are presumably related to the nanocrystal–amorphous-matrix interface states. The proposed approach can be used to produce light-emitting diodes on non-refractory substrates.},
doi = {10.1134/S1063782616070101},
journal = {Semiconductors},
number = 7,
volume = 50,
place = {United States},
year = {Fri Jul 15 00:00:00 EDT 2016},
month = {Fri Jul 15 00:00:00 EDT 2016}
}
  • Dark conductivity in amorphous silicon {ital p}-{ital i}-{ital n} devices arising from thermal generation through bulk defect states is explored. The current decays slowly after a voltage is applied, due to depletion of charge from the undoped layer, and is voltage dependent due to a field-enhanced generation rate. Creation of metastable bulk defects by light soaking reversibly increases the current. The steady-state generation current is dervied from the measured relaxation time and depletion charge.
  • The determination of the ambipolar diffusion length within the i layer of a p-i-n structure made of hydrogenated amorphous silicon is reported for the first time. It is shown that this important parameter can be determined by measurements carried out on the entire structure. One finds for a typical cell structure that the measured diffusion length is 10--20% smaller than the true i-layer value.
  • The origin of the difference in the open circuit voltage V/sub oc/ between a p-i-n and n-i-p type hydrogenated amorphous silicon solar cells is discussed theoretically, considering the interaction of photogenerated free electrons and holes, i.e., the effect of a self-field. It has been clarified that the self-field aids the carrier collection in an n-i-p cell whereas it impedes the carrier collection in a p-i-n cell. This difference in the effect of the self-field on the photovoltaic process causes the difference in V/sub oc/ between these two type cells.
  • Current-voltage (I-V) characteristics of p-i-n structures based on amorphous silicon ({alpha}-Si:H) with small hole diffusion lengths (shorter than the thickness of the i-layer of a p-i-n structure) have been experimentally studied with and without illumination. It is shown that forward I-V characteristics of structures of this kind can be described by a dependence inherent in diodes, with a diode ideality factor two-three times the maximum value of 2, theoretically predicted for generation-recombination currents in p-n junctions. The dark current is always substantially lower than the photocurrent in a cell biased with a voltage approximately equal to the opencircuit voltage ofmore » the photocell. Dark currents cannot contribute to the I-V characteristic under illumination. The photocurrent decreases with increasing photovoltage at a bias lower than the open-circuit voltage because of a decrease in the collection coefficient and the increasingly important role of back diffusion of electrons into the p-contact, rather than as a result of the dark injection. In the case of biases exceeding the open-circuit voltage, back diffusion becomes the predominant component of the current.« less
  • The transport simulations provided by the computer program AMPS have been used to give an in-depth analysis of the role of the {ital p}-layer contact barrier height, contact transport mechanism, {ital p}-layer thickness, and {ital p}-layer quality on the performance of hydrogenated amorphous silicon {ital p}-{ital i}-{ital n} solar cells. We demonstrate for the first time that, if the contact barrier height to the {ital p}-layer is below a critical value and if tunneling through the {ital p}-layer is not important, then the performance of cells with either active or dead {ital p}-layers varies with contact barrier height regardless ofmore » {ital p}-layer thickness. We show that, even for an optimistic {ital p}-layer active doping density of 10{sup 19} cm{sup {minus}3}, this critical barrier height is high ({similar to}1.2 eV). Our analysis implies that one of two situations must occur in an actual {ital a}-Si:H {ital p}-{ital i}-{ital n} structure: the {ital p}-layer contact plays an important role in determining cell efficiency, or the tunneling of holes through the front contact/{ital p}-layer interface must be important. Comparison of simulated results, with and without tunneling, with experimental data suggests that tunneling is occurring in actual devices and is important in efficient structures.« less