Faculté des sciences

Electrical properties and degradation kinetics of compensated hydrogenated microcrystalline silicon deposited by very high-frequency-glow discharge

Flückiger, R. ; Meier, J. ; Goetz, M. ; Shah, Arvind

In: Journal of Applied Physics, 1995, vol. 77, no. 2, p. 712-716

Microcrystalline silicon (µc-Si:H) layers deposited by the very high-frequency-glow discharge technique at a radio-frequency excitation of 70 MHz are observed to be basically slightly n type. By doping (so-called ``microdoping'') with boron in the gas phase volume part per million (vppm) range, compensated material could be obtained. The influence of this doping on the electronic... Plus

Ajouter à la liste personnelle
    Summary
    Microcrystalline silicon (µc-Si:H) layers deposited by the very high-frequency-glow discharge technique at a radio-frequency excitation of 70 MHz are observed to be basically slightly n type. By doping (so-called ``microdoping'') with boron in the gas phase volume part per million (vppm) range, compensated material could be obtained. The influence of this doping on the electronic transport properties is documented. A pronounced onset of the boron incorporation into the films measured by secondary-ion-mass spectrometry is observed around 3 vppm (B2H6/SiH4), together with marked changes in the electrical properties. The compensated film obtained for a microdoping of about 1 vppm shows the lowest dark conductivity [3×10−8 (Ω cm)−1], the highest activation energy (517 meV), and, finally, the highest photoconductive gain of 6×103 (photo/dark current ratio). Depending on the value of the activation energy (the critical value is  0.2 eV), two different transport models are identified, corresponding to ``Meyer–Neldel'' or ``anti-Meyer–Neldel'' behavior. As for light-induced degradation, the compensated film exhibits better stability than undoped films. Finally, the use of slightly boron doped µc-Si:H as photovoltaically active material will be discussed.