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

p-Type glow discharge hydrogenated amorphous silicon films with nearly plac ed (similar to 5 mu m) coplanar metallic electrodes were led to breakdown u nder 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 i n the films. A thermal model is shown to fit reasonably the electrical beha vior of samples prior to breakdown. Two parts are developed in this approxi mation: the first one assumes that during the initial homogeneous heating o f the semiconductor due to Joule effect, stationary states are reached. The heat is assumed to dissipate from the metallic contacts through a Newtons convection mechanism. From the experimental data and the model proposed, th e I-V plot is fitted, the heat transfer area and constant are calculated an d 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 estim ate of the time required by the sample to reach a certain steady-state limi ting temperature above which much faster heating produces breakdown. This t ime correlates well to the delay time reported in the literature. (C) 3000 Elsevier Science Ltd. All rights reserved.