Fabrication of Electron-Bombarded Semiconductor (EBS) diodes

This report is a complete description of the design criteria and the processes used for the fabrication of electron-bombarded semiconductor diodes for Class C operation at 2.1 GHz and lower frequencies. The devices are planar p-n junction diodes fabricated on n/n(+) epitaxial material with a deep diffused guard ring surrounding the thin junction which the electron beam penetrates. Leakage currents are sufficiently low so that thermal runaway does not occur until the device temperature exceeds 350C. It is demonstrated that a Schottky barrier is not a good choice for these large area power devices due to higher leakage current, and that a p-n junction is to be preferred. However, a layer of metal was needed to reduce the net sheet resistance of the thin p+ junction and a thin (approximately 300A) sputtered film of molybdenum was shown to be a good choice in this case. The use of Mo-Au metalization proved to be a simple and reliable system for these devices. (Modified author abstract)