Book/Report

FZJ-2018-06949

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Ladungsträgertransport- und Rekombinationsuntersuchungen an pin-Dioden aus amorphem Silizium (a-Si:H) im Vorwärtsstrombetrieb

Becker, F. (Corresponding author)FZJ*

1994
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/20263

Report No.: Juel-2949

Abstract: The transport and recombination in hydrogenated amorphous silicon (a-Si:H) pin-diodes is investigated by its forward current densities, electroluminescence and optical properties. The diodes mainly consist of p-doped (p), intrinsic (i) and n-doped (n) amorphous silicon layers. The EL-quantum efficiency is constant at increasing forward bias, i. e. the current is a pure recombination current. Time resolved measurements reveal the following: After applying a rectangular voltage pulse a space charge limited current is followed by a double injection recombination current with a delay time. The dependence of the delay time on various parameters, e. g. the puIs repetition rate, the temperature and the voltage between the pulses is discussed in this work. Simultaneously transients of the electroluminescence were measured, which show the beginning of the recombination with a certain delay time. These delay times are a measure of the average radiative lifetime (about 1 $\mu$s at room temperature). The nonradiative lifetime can be calculated being less than Ins by taking the low quantum efficiency. Amorphous silicon has localized states in the band gap. This causes the trapping of charged carriers of the previous pulse in these states leading to a residual space charge. A high pulse repetition rate leads to a faster current rise due to these carriers. This can be seen more pronounced at low temperatures, because the thermal emission rate from the localized states in the extended states decreases. Although the drift mobility of both charge carriers decreases with increasing temperature, the delay of the current rise at a constant applied voltage decreases below about 200K, because of the trapping effect. A series of pin-diodes with different i-layer thickness show, that the drift mobility of the holes is 2 · 1O$^{-3}$ cm$^{2}$V$^{-1}$s$^{-1}$ at room temperature. If no charged carriers remain in the sample, the delay time between the onset of the voltage and the recombination current is determined by the drift mobility of the holes. From the temperature dependence an activation energy of 0.57eV is obtained. By comparison of the interference fringes of measured spectra with calculated spectra spectrally resolved EL-measurements reveal, that the EL in the temperature range 78K<T<300K is generated in the i-layer very close to the p/i-contact. Although the spectra shift to higher energies with decreasing temperature or increasing current density, the thickness of the emission layer does not change significantly and remains located very close to the p/i-contact.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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Database coverage:

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