Virtual cathode apparition in Pt/a-Si:H Schottky barrier under illumination and applied voltage

¹ Département d'Électronique, Faculté des Sciences et Sciences de l'Ingénieur, Université de Mostaganem, 27000 Mostaganem, Algeria
² Département de Physique, Université d'Oran, Es-Sénia 31100, Algeria

Corresponding author: aziz_boukra@yahoo.fr

Received: 5 October 2007
Revised: 22 February 2008
Accepted: 20 March 2008
Published online: 6 May 2008

Abstract

The behavior of illuminated Pt/a-Si:H Schottky barrier has been studied by numerical calculations. The electric field, the electrons and holes currents, the charge space and the recombination rate where calculated as function of the position. The photocurrent, when the front of the barrier is illuminated by different wavelengths under lower reverse applied voltage, tends towards saturation. By comparing the number of collected carriers to the incoming photons, we remark that the collection of photogenerated carriers is partial for long wavelengths (λ ≥ 600 nm), in this case the collection efficiency is determined by the recombination in the bulk, and total when the short wavelengths (λ < 600 nm) are used and the recombination in the front layer seems to be an important carrier loss mechanism. This is mainly the consequence of the virtual cathode apparition that behaves against the carrier collection. This cathode moves to back contact and tends to disappear with increasing the reverse bias voltage.