Cold Cathode Devices Based on Negative Electron Affinity Materials

Cold cathode devices capable of emitting electrons into a vacuum without relying on high temperature thermionic emission are expected to play an important role in a wide variety of applications ranging from high frequency, high power amplifiers to flat panel displays. Cold cathode devices based on negative electron affinity materials rely on semiconductors for which the barrier between electrons in the conduction band and the vacuum level (electron affinity) is negligible. Thus, all the electrons (in the conduction band) reaching the surface of such devices can be swept out into the vacuum. Such devices are expected to provide stable, high-performance operation, even in relatively low vacuum conditions. Recent experimental evidence indicates that several wide bandgap semiconductors, most notably diamond and AlN exhibit an intrinsic negative electron affinity. AlN is particularly interesting because it is nearly lattice matched to SiC and hence may be combined with SiC devices and grown on SiC substrates. In addition, AlGaN alloys will be near perfectly lattice matched, allowing for the use of heterostructures in such devices. In this Phase I project, efficient negative electron affinity devices based upon AlN will be demonstrated.