Electron emission from CVD diamond p–i–n junctions with negative electron affinity during room temperature operation

We successfully observed electron emission from hydrogenated diamond p–i–n junction diodes with negative electron affinity during room temperature operation. The emissions started when the applied bias voltage produced flat-band conditions, where the capacitance–voltage characteristics showed carrier injection in the i-layer. In this low current injection region, the electron emission efficiency (η) of the p–i–n junction diodes (p is top layer) was about 5 × 10− 5, while that of the n–i–p diodes (n is top layer) was about 10− 8. With increasing diode current, both diodes showed an increase in η and a nonlinear increase in emission current. In the high current injection region with high diode current of 5–50 mA, both diodes had an emission current of almost 10 μA, where η of a p–i–n junction diode was 0.18%, while that of a n–i–p junction diode was 0.02%.Note that η, which corresponds to the electron emission mechanism, depended on the diode current level.

Research highlights
► Electron emission of 8.8-10 μA from diamond p-i-n junction diodes with negative electron affinity was obtained.
► The top layers facing to the collector electrodes were a p layer or an n layer.
► In low injection region, a p-top diode exhibited 5000 times larger efficiencies (η) than that of an n-top diode.
► However, increasing of the diode current increased both η’s, and closed to each.
► Note that η, which corresponds to the electron emission mechanism, depended on the diode current level.