Evaluation of Wide-Bandgap Semiconductors as Robust Cold-Cathode Electron Emitters for Application in Vacuum Electron Devices

Microwave Power Technology, with support from the David Sarnoff Research Center and Wayne State University, proposes to evaluate new wide-bandgap semiconductor cold-cathode electron emitters in practical device configurations. Recent work at the supporting organizations indicates the possibility of stable robust cold-cathode emission from Diamond coated with BN at current densities above 1 A/cm2 and at pressures as high as 10-4 torr. These results significantly exceed any reported by others working with surface emitters and the robustness far exceeds what has been achieved with point emitters. The objective of this program will be to test these materials at current densities and under processing and operating conditions suitable for military electron devices riuch as microwave amplifiers, EBS devices, flat-panel displays, compact e-beam excited lasers, and high-power switches. During this project, a number of metal-ceramic diodes and triodes will be constructed, some with phospor screens and glass windows, to characterize both the uniformity and stability of the emission characteristics from these materials. It is the intent of this program to develop new information on peak emission capability, high-power CW operation, emission pressure dependence, and emission stability with lifetime. A successful cold-emitter will lead to far more compact and robust microwave amplifiers, EBS devices, and other electron devices used in both military and commercial systems. Further to flat-panel displays that are higher efficiency, greater brightness, and a wider temperature range than possible with any competing technology. The early work on the BN/Diamond combination makes it appear as the best candidate for all of these future applications.