Electron emission from GaN/LaB6 cold cathodes

Summary form only given, as follows. Recent developments in vacuum microelectronics have led to a resurgence of interest into cold cathode emission for applications to a variety of electronic devices. For these new applications, the ideal cold cathode should have the following characteristics: (i) low-voltage operation (5-20 volts); (ii) high current density (5-10 A/cm2); (iii) room temperature operation; and (iv) stable and durable operation. Effective Negative-Electron-Affinity (NEA) and Optoelectronic Cold Cathode (OECC) structures have been fabricated using a combination of the wide-bandgap semiconductors, GaN and AlGaN, and the low work function metal, LaB₆. In the NEA structure, electrons are injected from an n-type GaN layer into a thin p-type GaN layer. Appropriate design of the p-type thickness, which was guided by Monte Carlo transport simulations, allows some fraction of the injected electrons to arrive at the p-GaN/LaB₆ interface with enough energy to traverse the thin LaB₆ layer and emit into vacuum. In the OECC, photons are generated at a p-n junction in GaN. The photons are subsequently absorbed by a LaB₆ layer, creating electrons with sufficient energy (3.4 eV) to overcome the LaB₆ work function of ~2.5 eV. The GaN and LaB₆ fabrication is discussed in detail. Results of the photoemission from thin LaB₆ films and electron emission from hybrid and monolithic cold cathodes are discussed