Observation of Electronic Band-Structure Effects on Impact Ionization by Temperature Tuning

Abstract

Impact ionization in semiconductors is shown to be strongly affected by temperaturetuning the band structure. In $〈100〉$ GaAs between 25 and 150\ifmmode^\circ\else\textdegree\fi{}C the hole ionization rate $\ensuremath{\beta}$ is greater than the electron rate $\ensuremath{\alpha}$, whereas above this temperature $\ensuremath{\alpha}$ becomes greater than $\ensuremath{\beta}$. This effect is attributed to the sudden lowering of the electron threshold ionization energy close to 200\ifmmode^\circ\else\textdegree\fi{}C and is shown to be evidence for the existence of the pseudogap between the ${\ensuremath{\Gamma}}_{6}\ensuremath{-}{X}_{6}$ and ${\ensuremath{\Gamma}}_{7}\ensuremath{-}{X}_{7}$ conduction bands.