Terahertz Frequency Signal Detector Based on an Antiferromagnetic Tunnel Junction at Room and Cryogenic Temperatures

Abstract

Cooling to cryogenic temperatures is widely used for improving the performance of various types of signal detectors. In this paper we theoretically analyze the performance of a prospective detector of (sub-)terahertz-frequency (TF) signals based on an antiferromagnetic tunnel junction (ATJ) $\mathbf{Pt}/\mathbf{Ir}_{0.2}\mathbf{Mn}_{0.8}/\mathbf{MgO}/\mathbf{Pt}$ employing the tunneling anisotropic magnetoresistance (TAMR) effect. Using a simple theoretical model, where the $\mathbf{MgO}$ tunneling barrier thickness, junction resistance, and TAMR ratio are considered as temperature-dependent values, we show that there are two distinct regimes of detector operation, although in both these regimes the detector output DC voltage $\boldsymbol{U}_{\mathbf{DC}}$ weakly depends on the temperature $\boldsymbol{T}$, One of these regimes, observed at rather large signal frequencies $\boldsymbol{f > 0.5}\ \mathbf{THz}$, is characterized by the monotonic, almost linear dependence of UDC on $\boldsymbol{T}$, however, in another, low-frequency regime $(\boldsymbol{f\sim 0.1}$ THz), the output DC voltage increases with a reduction of temperature. Such a behavior can be explained by the temperature dependence of intrinsic junction's resistance and capacitance, which, in turn, do influence on detector's inertial properties and its matching to an external 50 Ohm circuit. Obtained results demonstrate that cooling of ATJ-based signal detector can be useful only for devices operating at rather low frequencies lying in the sub-TF band.