Fundamentals of Photoemission from Wide Gap Materials

It is well known that the Einstein’s photoelectric effect occupies a singular position in the whole arena of materials science and related disciplines in general together with the fact that the photoemission from the electronic materials is also a vital physical phenomenon from the viewpoint of modern optoelectronics and photoemission spectroscopy [1]. The classical equation of the photo-emitted current density is [2] $J = \left[ {{{4\pi em^\ast g_v \left( {k_B T} \right)^2 } \left/\right. {h^3 }}} \right]\exp \left[ {{{\left( {h\nu - \phi } \right)} \left/\right. {\left( {k_B T} \right)}}} \right]$, where e e e e , $m^\ast$, g g g g _{v v v v} , k k k k _{B B B B} , T T T T , h h h h , $h\upsilon$ and $\phi$ are the electron charge, effective electron mass at the edge of the conduction band, valley degeneracy, the Boltzmann constant, temperature, the Planck’s constant, incident photon energy along z z z z -axis and work function, respectively. The aforementioned equation is valid for both the charge carriers, and in this conventional form it appears that the photoemission changes with the effective mass, temperature, work function, and the incident photon energy, respectively. This relation holds only under the condition of carrier nondegeneracy.