Sn-nanothreads in GaAs matrix and their sub- and terahertz applications

Abstract

We report on theoretical and experimental studies of gated GaAs structures like the field-effect transistor with an array of parallel Sn nanothreads (Sn-NTs) embedded into GaAs matrix. Two device structures are proposed and considered: the pseudomorphic HEMT (PHEMT) with a doping profile of Sn-NTs and the terahertz hot-electron bolometer (THz HEB) both fabricated on vicinal GaAs substrates. PHEMT demonstrates the anisotropy of drain-source current I∥/I⊥ ~ 2.5 at 300 K when current flows along and across Sn-NTs which we relate to formation of quasi-one-dimensional conductivity channels in InGaAs quantum well. Maximum power gain cut-off frequency fmax ~ 0.15 THz is shown. The operation of THz HEB is associated with an increase in the density of the delocalized electrons due to their heating by the incoming THz radiation. The quantum and the classical device models are developed. Since the fraction of the delocalized electrons strongly depends on the average electron energy (effective temperature), the proposed THz HEB can exhibit an elevated responsivity compared with the HEBs based on more standard heterostructures. Due to a substantial anisotropy of the device structure, the THz HEB may demonstrate a noticeable polarization selectivity of the response to the in-plane polarized THz radiation.