Electron emission from diamond p-i-n junction diode with heavily P-doped n+ top layer

We found clear improvement in electron emission performances in low injection region of hydrogenated diamond p-i-n junction diodes with heavily phosphorous-doped (P-doped) n(+) top layer, where the top layer faced to a collector electrode. The emission started just below 4.5 V, that is the built-in potential expected as diamond p-n junction diode with boron acceptors and phosphorous donors. In this flat-band condition, the electron emission efficiency (n) reached to 0.2% during room temperature (RT) operation, and eta > 1% during 573 K operation were obtained, whereas, the previous diamond p-i-n junction diode without the heavily P-doped top layer showed eta < 10(-6)% in these temperature ranges. In such low injection region, the results indicated that direct emission of electrons injected from n-layer to i-layer contributed to the electron emission. With high diode current I-d = 80 mA, we obtained the highest emission net current I-e = 78 mu A up to now, and the eta = 0.1% during RT operation. A dependence of eta upon the forward diode current suggested that there were two electron emission mechanism in the same sample. Electroluminescence results suggested that exciton-derived electron emission might be concerned in the high current injection region. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim