Abstract
Theoretical studies and numerical simulations on design, performance, and improvements of terahertz quantum-well photodetector (THz QWP) are presented. In the first part of this paper, we discuss the device band structure resulting from a self-consistent solution and simulation results. First, the temperature dependence of device characteristics is analyzed. Next, we deduce the condition of optimal doping concentration for maximizing dark current limited detectivity Ddet* when QWP is lightly doped. Accordingly, unlike in previously published reports, doping concentration is not fixed and is selected by the above condition. In the second part of this paper, we propose two schemes for improving operation temperature. The first is to incorporate an optical antenna which focuses incident THz wave. Numerical results show that the QWP with peak frequency higher than 5.5 THz is expected to achieve background-noise-limited performance at 77 K or above when employing a 106 times enhancement antenna. The second scheme is to use a laser as the signal source to achieve photon-noise-limited performance (PLIP) at high temperatures. Simulations show that when operating below critical temperature QWPs in the range of 1 ∼ 7 THz can reach PLIP under practical illumination intensities.
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