Enhancement of terahertz electromagnetic wave emission from an undoped GaAs/n-type GaAs epitaxial layer structure

We have investigated the emission of the terahertz electromagnetic wave from an undoped GaAs (200 nm)/n-type GaAs (3 mu m) epitaxial layer structure (i-GaAs/n-GaAs structure), where the doping concentration of the n-GaAs layer is 3 x 10(18) cm(-3). It is found that the first-burst amplitude of terahertz wave of the i-GaAs/n-GaAs sample is remarkably larger than that of a n-GaAs crystal, which means that the i-GaAs layer enhances the terahertz emission intensity. The first-burst amplitude of the i-GaAs/n-GaAs sample, by tuning the pump-beam energy to the higher energy side, exceeds that of an i-InAs crystal that is known as one of the most intense terahertz emitters. We, therefore, conclude that the i-GaAs/n-GaAs structure is useful to obtain intense terahertz emission. (C) 2008 American Institute of Physics.