IMPROVED COLD ELECTRON-EMISSION CHARACTERISTICS OF ELECTROLUMINESCENTPOROUS SILICON DIODES

The property of electroluminescent porous silicon (PS) diodes as surfa ce-emitting cold cathodes were investigated. The experimental PS diode s consist of thin Au films, PS, n(+)-type Si substrates, and ohmic bac k contacts. When a positive bias voltage V-PS is applied to the Au ele ctrode with respect to the substrate, electrons are uniformly emitted through the Au contact as well as photons. The cold electron emission characteristics are presented here in terms of the PS layer thickness dependence, effects of rapid thermal oxidation (RTO), and electrolumin escence (EL) characteristics. It was demonstrated that both the decrea se in the PS layer thickness (d(PS)) and the introduction of RTO treat ment are useful for a significant improvement in the emission characte ristics, and that the emission current and efficiency for a RTO-treate d diode with d(PS)=3 mu m reach 450 mu A/cm(2) and 0.2%, respectively, at V-PS=27 V. It is also shown that in every case, the Fowler-Nordhei m scheme holds in the bias voltage dependence of the emission current. The emission mechanism based on the high-field effect near the outer surface of PS layer, is discussed in relation to the visible EL emissi on. (C) 1997 American Vacuum Society. [S0734-211X(97)01205-5].