Thermal model for breakdown in p-type hydrogenated amorphous silicon films with coplanar electrodes

Abstract

p-Type glow discharge hydrogenated amorphous silicon films with nearly placed (∼5 μm) coplanar metallic electrodes were led to breakdown under the effect of voltage bias. Non-ohmicity in the I– V plot was analyzed in order to look for the transport mechanism helping to produce breakdown in the films. A thermal model is shown to fit reasonably the electrical behavior of samples prior to breakdown. Two parts are developed in this approximation: the first one assumes that during the initial homogeneous heating of the semiconductor due to Joule effect, stationary states are reached. The heat is assumed to dissipate from the metallic contacts through a Newton's convection mechanism. From the experimental data and the model proposed, the I– V plot is fitted, the heat transfer area and constant are calculated and the temperature–voltage plot is determined. In the second part, the heat conduction equation along the distance between the contacts is numerically solved in one dimension with this information. The result provides an estimate of the time required by the sample to reach a certain steady-state limiting temperature above which much faster heating produces breakdown. This time correlates well to the delay time reported in the literature.