Thermally enhanced photoinduced electron emission from nitrogen-doped diamond films on silicon substrates

Abstract

This work presents a spectroscopic study of the thermally enhanced photoinduced electron emission from nitrogen-doped diamond films prepared on $p$-type silicon substrates. It has been shown that photon-enhanced thermionic emission (PETE) can substantially enhance thermionic emission intensity from a $p$-type semiconductor. An $n$-type diamond/$p$-type silicon structure was illuminated with $400--450$ nm light, and the spectra of the emitted electrons showed a work function less than 2 eV and nearly an order of magnitude increase in emission intensity as the temperature was increased from ambient to $\ensuremath{\sim}400 \ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. Thermionic emission was negligible in this temperature range. The results are modeled in terms of contributions from PETE and direct photoelectron emission, and the large increase is consistent with a PETE component. The results indicate possible application in combined solar/thermal energy conversion devices.