New Results on the Gold-Silicon Surface Barrier

The effects of certain new combinations of etch quenchants and surface treatments on the rectification characteristics of the gold-n-silicon surface barrier are described. Reverse currents of less than 1 ¿A/cm2 at 1500 volts bias at room temperature have been obtained with 450 ohm-cm silicon without using encapsulaticn or a guard ring structure and without prolonged aging. It is shown that differential capacitance measurements performed for determining the height of the surface potential barrier may be unsuccessful or inaccurate due to slow charge migraticn on the surface. Field effect measurements were performed and the surface potential and density of ionized fast states were obtained therefrom. A new ambient cycle was evolved in order to obtain the conductance minimum in the field effect measurements. It is shown that the best rectification characteristics are obtained not when an inversion layer is formed at the silicon surface but when a depletion layer is formed of just the right amount to make the surface conductance close to its minimum value. Surface treatments giving rise to strong inversion layers were found to consistently yield poor diodes. The correlation of the rectification characteristics to the density of fast states and to the thickness of the interfacial layer is discussed. The role of air and moisture in the formation of the diode is explained. A simple model of the surface barrier is presented which explains many of the observed effects.