Surface Effects of Gaseous Ions and Electrons on Semiconductor Devices

Previous investigations have indicated that radiation surface effects on semiconductors largely are due to ions produced in the gas near the semiconductor surface. In the present work these effects have been studied directly by a gas discharge technique. Large electrical changes could be induced by either positive or negative species; in the case of transistors Ico could increase by several orders of magnitude. The relaxation of the effects may take many hours. The nature of the surface effects was investigated by observations of the I-V characteristics and of the action of various gases (e.g. O2,H2O) after ion exposure. The main effects were due to inversion layers which might be induced on either side of a junction. The decay of the surface effect could be accelerated by heat, light and by the presence of certain gases. In addition the surface charge could be removed very rapidly by exposure to species of opposite charge to those creating the inversion layer.