Development of an active-matrix "HEED" cold cathode and its application to an image sensor
For practical advantages of the HEED (high-efficiency electron emission device) such as a low driving voltage, a high emission current density, especially application to an ultra high sensitive compact image sensor can be expected. A prototype active-matrix HEED image sensor integrated with scanning driver circuits was developed with a HARP (high-gain avalanche rushing amorphous photoconductor) target. It was demonstrated that the prototype 256 times 192 pixels active-matrix HEED array operates well as an effective probe for high-resolution image pickup under dim lighting. The possibility of the active-matrix HEED for development of next-generation image sensor with ultra high sensitivity and high definition was concluded in this report
High Efficiency Electron-Emission in Pt/SiOx/Si/Al Structure
A high efficiency electro-emission device (HEED) has been developed with a structure of Pt/SiOx /Si/Al on a thermally-oxidized Si substrate. The thicknesses of the SiOx and Si films were 400 nm and 5 µ m, respectively. Electron emission characteristics of the HEED are reported. It was found that the HEED has an electron-emission efficiency as high as 28% and a high brightness of 80 kcd/m2 using phosphor ZnS:Cu,Al. This high electron-emission efficiency was obtained in a range of applied voltage in which negative resistance occurred.
Cold Electron Emission from Electroluminescent Porous Silicon Diodes
It is demonstrated that electroluminescent porous silicon (PS) diodes operate as surface-emitting cold cathodes. The PS diode is composed of a semitransparent thin Au film, PS layer, n-type Si substrate and ohmic contact. When a sufficient positive bias voltage is applied to the Au contact in vacuum, the diode uniformly emits electrons as well as visible light. This cold emission is explained by the model that electrons are injected from the substrate, drifted by the field within the PS layer, and ejected as hot electrons through the thin Au film. This mode gives important insight for understanding the electroluminescence mechanism of PS, and shows the potential of PS devices not only for optoelectronic applications, but also for vacuum microelectronic ones.