Intense emission of terahertz electromagnetic wave from an undoped GaAs/n ‐type GaAs epitaxial layer structure

Abstract

We have investigated the emission of the terahertz (THz) electromagnetic wave from an undoped GaAs (200 nm)/n ‐type GaAs (3 μm) epitaxial layer structure (i ‐GaAs/n ‐GaAs structure), where the doping concentration of the n ‐GaAs layer is 3 × 1018cm‐3. It is found that the first‐burst amplitude of THz wave of the i ‐GaAs/n ‐GaAs structure is considerably stronger than that of an n ‐GaAs crystal, which means that the i ‐GaAs layer enhances the THz emission intensity. The first‐burst amplitude of the i ‐GaAs/n ‐GaAs structure, by tuning the pump‐beam energy to the higher energy side, exceeds that of an i ‐InAs crystal known as one of the most intense THz emitters. We, therefore, conclude that the i ‐GaAs/n ‐GaAs structure is useful to obtain intense THz emission. From the pump‐beam energy dependence of the first‐burst amplitude, the THz‐emission mechanism of the i ‐GaAs/n ‐GaAs structure is attributed to the surge current of the photogenerated carriers flowing through the i ‐GaAs layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)