Dopant Migration-Induced Interface Dipole Effect in n-Doped GaAs/AlGaAs Terahertz Detectors

A heterojunction interfacial workfunction internal photoemission (HEIWIP) terahertz detector with~\!\!1\!×\!10¹⁸\ cm⁻³n-type doped GaAs emitters in a multilayerGaAs/Al0.13Ga0.87 Asheterostructure is presented. The detection mechanism is based on free carrier absorption with a broad response extending to~5.26 THz (57), corresponding to an effective workfunction of~21.8 meV, which is much smaller than the offset expected for an Al fraction ofx = 0.13at a1 × 10¹⁸\ cm⁻³doping. This is attributed to a reduction of the conduction band offset by interface dipole formation between the accumulated negative charges at the interface states and migrated positively charged donors in the barrier. The device has a peak responsivity of 0.32 A/W at~\!\!26 5 K. It is demonstrated that the dopant migration-induced interface dipole effect can be used to extend the zero response threshold frequency(f₀)of n-type HEIWIP detectors.