Amorphous SiNx:H thin film diodes (TFDs) can be used for pixel addressing in active matrix liquid crystal displays. They depend on the application of high electric fields to switch from the ‘off to the ‘on’ states. They prove to be remarkably rugged and can be made with high yield and tolerance. An important feature that contributes to this ruggedness is the ability of these switches to generate defect states at a rate dependent on current density. Current induced defect states trap electrons and cause a reduction in field at the cathode contact, which in turn causes a reduction in current density. Therefore, current will be transferred from regions of high current to regions of low current in the device, making the current flow more uniform. TFDs with thin regions will become effectively thicker during current stressing. In order to check this hypothesis, thin film diodes with nonuniform thickness a-SiNx:H layers were current stressed, and the I-V characteristics compared with those calculated using a defect generation model. The experimental data agreed well with our theoretical model.