APPLICATION OF p-n JUNCTIONS BASED ON GALLIUM ARSENIDE WITH SULFIDE-MODIFIED SURFACE AS AMMONIA SENSORS

The effect of sulfide surface treatment modes on the volt-ampere characteristics of forward and reverse currents and the sensitivity of GaAs-based p-n junctions to ammonia vapor was investigated. It was found that short-term treatment reduces forward and reverse currents in the pre-breakdown region measured in air and leads to an increase in sensitivity to ammonia vapor. The decrease in the currents of the original structures measured in air after sulfide treatment is explained by a decrease in the density of surface centers due to the removal of the oxide layer. The reason for the sensitivity of GaAs-based p-n structures to ammonia vapor is the formation of a surface conduction channel that short-circuits the p-n junction and leads to an increase in forward currents in the region of low injection levels and reverse currents in the pre-breakdown region. Short-term sulfide treatment, by reducing the density of surface centers, increases the number of free electrons in the channel, which leads to an increase in the sensitivity of the treated structures to ammonia vapor. An increase in the processing time is accompanied by the appearance of new surface centers and a decrease in the maximum sensitivity to ammonia vapor.