EFFECT OF WATER VAPORS ON THE TIME-RESOLVED SURFACE CURRENT INDUCED BY AMMONIA MOLECULES ADSORPTION IN GaAs P-N JUNCTIONS

Abstract

The time-resolved surface current in an n-conducting channel, due to ammonia and water molecules adsorption in GaAs p-n structures was studied. It is shown that the presence of water vapors in the ambient atmosphere strongly affects the current decay curves after the ammonia vapors removal. The current decay curve in this case has three exponential components with different characteristic times: τ1 = 30 s, τ2 = 1900 s and τ3 = 9400 s, as well as a component with τ4 >> τ3. The results are explained in terms of a simple model taking into account a dynamic equilibrium between the free electrons in the conducting channel and electrons on slow surface centers. Each decay curve exponential component is due to the emptying of corresponding centers. The characteristic time of a current decay curve exponential component is determined by the depth and density of the corresponding surface levels, as well as the conducting channel thickness.