Detection of terahertz radiation in gated two-dimensional structures governed by dc current

Abstract

We present theoretical and experimental studies of the direct current effect on the detection of subterahertz and terahertz radiation in gated two-dimensional structures. We developed a theory of the current-driven detection both for resonant case, when the fundamental frequency of plasma oscillation is large compared to inverse scattering time, omega(0)tau >> 1, and for the nonresonant case, omega(0)tau << 1, when the plasma oscillations are damped. We predict that, in the nonresonant case, even a very small dc current would increase the detection amplitude up to two orders of magnitude. Physically, this increase is related to an abrupt transition from the linear to saturation region near the knee of the current-voltage characteristic. When the current increases up to the saturation value, the electron concentration near the drain becomes very low and can be strongly affected by a small external field. As a consequence, the two-dimensional channel becomes extremely sensitive to external perturbations. In the resonant case, the detection amplitude has maxima when the radiation frequency is equal to fundamental plasma frequency and its harmonics. We predict that the effective linewidths of the respective resonances would decrease with the increasing current. Physically, this happens because dc current shifts the system towards the plasma wave instability. At some critical current value, the width corresponding to the fundamental frequency would turn to zero, indicating the onset of plasma waves generation. Our experimental measurements performed on GaAs HEMT confirm the theoretical predictions

Enhanced terahertz detection using multiple GaAs HEMTs connected in series

“…We proved this experimentally: no response was detected without dc current flow in a symmetrical transistor (compare to [23]). The flow of dc current in this transistor creates asymmetry in boundary conditions at source and drain, asymmetry for propagation of plasma waves, and this asymmetry enhances plasma wave detection in the device [21]. In the saturation mode, asymmetry across the transistor channel increases and consequently the nonresonant THz response increases.…”

“…The 0.5 µm enhancement-mode InGaAs/GaAs HEMT structures were fabricated by TriQuint Semiconductor. The main advantage of this technology is that it has a relatively high breakdown voltage that allows us to bias several transistors connected in series and guarantee that all of them operate in saturation region for the enhanced detection [21].…”

Wide modulation bandwidth terahertz detection in 130 nm CMOS technology

“…When current is driven to the drain terminal (currentdriven mode), the non-resonant, long channel plasmawave response increases sharply due to the increased channel asymmetry as described in reference [29]. The current driven response (valid only in the triode region) can be given as:…”

Влияние Высоты Барьера Затвор-Канал На Характеристики Детектирования Полевого Транзистора В Сверхвысокочастотном И Терагерцовом Диапазонах

“…[2-5] была продемонстрирована возможность де-тектирования на кремниевом транзисторе [6,7]. Хорошо развитая кремниевая технология позволяет интегриро-вать большое число транзисторов на единой пластине, делая возможным создание матричных приемников [8,9].Теоретическое описание процесса детектирования по-левого транзистора в СВЧ и ТГц диапазонах можно найти в работах [10][11][12][13][14][15]. На низких частотах, когда емкостной ток через переход затвор−канал пренебрежи-мо мал, можно пользоваться статическими уравнениями транзистора [10].…”

“…В этом случае удобно представлять транзистор в виде двухпроводной линии электропередачи, где одним проводником является затвор, а вторым -канал [13]. На частотах выше частоты релаксации импульса свобод-ных носителей заряда возможно резонансное детекти-рование, при этом движение носителей заряда в канале описывается уравнением Эйлера [11,12].Как правило, в полевых транзисторах ток проводи-мости через переход затвор−канал пренебрежимо мал. В случае контакта металл−полупроводник это экви-валентно большой высоте барьера Шоттки ( ∼ 1 eV).…”