It is shown that the voltage drift and light degradation in polymer light-emitting diodes are related and can be explained by the formation of traps and the modification of the space charge in the bulk of the polymer. The energy released by nonradiative carrier recombination is believed to be the driving force for the generation of traps in poly(p-phenylene vinylene) conjugated polymers. A first-approximation model is derived for the voltage drift and the light decrease during operation, which is in good agreement with experimental observations for time and current density dependencies.

Photon-emission experiments on silicon-rich hydrogenated amorphous silicon-nitride metal–semiconductor–metal diodes, have shown the existence of hot electrons under applied field strengths of approximately 106 V/cm. The effective temperatures and mean free path between collision for the electrons were estimated from the spectra. It is shown that, in general, asymmetrical changes in the electrical characteristics of the devices occur after prolonged dc stressing at high fields. Two drift mechanisms can be distinguished. The first is called ‘‘cathodic’’ drift and is driven by recombination between band-tail carriers in the semiconductor. The other is called ‘‘anodic’’ drift, and results from the effects of hot electrons at the anode. The spatial and time dependence of these drift mechanism is explained using a simple model.

The dc-current stress behavior of Mo/a-SiNxHy/Mo thin-film diodes is discussed for several a-SiNxHy-plasma-deposition conditions. Current transport is governed by thermionic field emission of electrons over a reverse biased Schottky barrier. The barrier height is determined by the a-SiNxHy-plasma-deposition conditions. Therefore these back-to-back Schottky devices provide an elegant way to perform dc-current stressing at several well defined carrier densities for similar stress fields. It is shown that such experiments allow assessment of defect-state creation/anneal mechanisms in a-SiNxHy. An electron-trapping-triggered anneal mechanism accounts for the observed dependence of the defect density at the electrode injecting contact (cathode) on the hole-barrier height at the anode. Also a new microscopically detailed anneal reaction scheme is proposed. The defect-state creation/anneal mechanism is expected to be generally applicable for all silicon-rich hydrogenated amorphous silicon alloys.

Hydrogenated amorphous-silicon–nitride thin-film diode (TFD) switches have been shown to degrade electrically at both the cathode (electron injection contact) and anode (noninjection contact) due, respectively, to electron–hole recombination and hot-electron-induced-state creation mechanisms. An antiparallel configuration of two asymmetric TFDs provides an elegant method to minimize the cathodic degradation and avoid the consequences of anodic defect state creation. In this way, extremely stable TFDs may be prepared.