THz Emission Induced by an Optical Beating in Nanometer-Length High-Electron-Mobility Transistors

Abstract

Experimental results of direct measurement of resonant terahertz emission optically excited in InGaAs HEMT channels are presented. The emission was attributed to two-dimensional plasma waves excited by photogeneration of electron-hole pairs in the HEMT channel at the frequency of the beating of two cw-laser sources. The presence of resonances for the radiation emission in the range of f 0 ± 10 GHz (with f 0 from 0.3 up to 0.5 THz) detected by a Si--bolometer is found. The intensity of THz emission exhibits a nonlinear growth with increase of the pumping power.

Investigation of high-frequency small-signal characteristics of FETs/HEMTs

“…As an example, figure 1 presents the current-voltage characteristics calculated for the above structure assuming the room temperature operation corresponding to the momentum relaxation rate ν = 3 × 10 12 s −1 . The obtained I-V curves and the threshold voltage of about U th = −0.3 to −0.35 V agree sufficiently well with available experimental and theoretical results for similar InGaAs HEMTs (see, e.g., [32,33,20,22] and references therein). Note that the I-V relations shown in figure 1 are stable both in voltage-and current-driven operations.…”

“…On the other hand, the excitation of 2D plasma waves by an external THz signal can be used for its detection [11]. This was widely discussed theoretically and confirmed experimentally [12][13][14][15][16][17][18][19][20][21][22]. Moreover, some experiments [18,22] devoted to the resonant detection of plasma waves and THz emission induced by optical beating, evidence that experimental conditions are already approaching DS-instability onset.…”

“…The former quantity describes the resonant detection effect. The latter gives the linear response amplitude, which, as was widely discussed (see, e.g., [18,22]), can describe the possibility of using the photo-excitation of 2D plasma waves as the source of the monochromatic THz radiation. The excitation level used in figure 12 corresponds to about 1-2% increase of the n-region concentration with respect to the dark level.…”

“…(i) DS instability of 2D plasma oscillations in conducting channels of FET/HEMT [7][8][9][10]; (ii) the detection of 2D plasma oscillations excited by external action [11][12][13][14][15][16][17][18][19][20][21][22].…”

“…Here, as a detecting signal any physical action able to excite in a resonant way the 2D plasma oscillations in the gated part of the FET/HEMT channel can be used. For example, the most often discussed cases are the direct electrical action [35] or the photo-excitation of electron-hole pairs in the FET/HEMT channel modulated by the beating frequency of two IR lasers in the THz frequency range (see, e.g., [14][15][16][17][18][19][20][21][22]35] and references therein).…”