Velocity-Modulation Transistor (VMT) –A New Field-Effect Transistor Concept

Sakaki, H.

doi:10.1143/jjap.21.l381

Cited by 145 publications

(41 citation statements)

References 6 publications

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“…Despite the susceptibility of black phosphorus to photo-oxidation [4], improvements to the electronic quality of black phosphorus devices has culminated in the observation of the quantum Hall effect [5]. In this work, we demonstrate the room temperature operation of a dual gated black phosphorus transistor operating as a velocity modulated transistor [6], whereby modification of hole density distribution within a black phosphorus quantum well leads to a two-fold modulation of hole mobility. Simultaneous modulation of Schottky barrier resistance leads to a four-fold modulation of transconductance at a fixed hole density.…”

mentioning

confidence: 92%

Dual-Gate Velocity-Modulated Transistor Based on Black Phosphorus

et al. 2016

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The layered semiconductor black phosphorus has attracted attention as a 2D atomic crystal that can be prepared in ultra-thin layers for operation as field effect transistors [1][2][3]. Despite the susceptibility of black phosphorus to photo-oxidation [4], improvements to the electronic quality of black phosphorus devices has culminated in the observation of the quantum Hall effect [5]. In this work, we demonstrate the room temperature operation of a dual gated black phosphorus transistor operating as a velocity modulated transistor [6], whereby modification of hole density distribution within a black phosphorus quantum well leads to a two-fold modulation of hole mobility. Simultaneous modulation of Schottky barrier resistance leads to a four-fold modulation of transconductance at a fixed hole density. Our work explicitly demonstrates the critical role of charge density distribution upon charge carrier transport within 2D atomic crystals.Black phosphorus (bP) is an elemental allotrope and a direct bandgap semiconductor with a puckered, honeycomb layer structure [7,8] that can be exfoliated down to atomic few-layer thickness [1-4, 9, 10]. Although bP is the most thermodynamically stable allotrope of phosphorus, photo-oxidation in the presence of water, oxygen and visible light is known to degrade bP with a reaction rate that increases as bP layer thickness decreases [4]. Several materials have been used to encapsulate bP in order to protect it against photo-oxidation, including hexagonal boron-nitride [11][12][13], aluminum oxide [14], parylene [4], and poly-methylmethacrylate [15]. Recent works have also shown that 2D hole transport can be achieved in a single 2D sub-band within an accumulation layer of many-layer bP [11,13,15], effectively combining 2D transport characteristics with the increased chemical stability of many-layer bP. These advances have culminated in the observation of the quantum Hall effect in bP [5]. Nonetheless, further understanding and control of transconductance, carrier mobility and contact resistance in bP field effect transistors (FETs) is desired.We report here an experimental investigation of the transport characteristics of bP FETs with an asymmetric dual gate geometry consisting of top and bottom gate electrodes. The top gate is found to be effective in modulating the back gate FET transfer characteristics, including both field effect mobility and Schottky barrier contact resistance. The mobility modulation effect enables operation of the dual gate bP FET as a velocity modulated transistor (VMT), first proposed by Sakaki [6] [18]. Asymmetric dual-gate bP FETs exhibit a two-fold mobility modulation at room temperature, and the underlying mechanism is modulation of hole density distribution with the naked bP quantum well channel of the bP FET, and a resultant modulation of scattering by charged impurities within the gate oxide, surface roughness, and other spatially dependent scattering mechanisms. Simultaneously, bP FETs exhibit strong Schottky barrier modulation. First conclusive...

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confidence: 92%

Dual-Gate Velocity-Modulated Transistor Based on Black Phosphorus

et al. 2016

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“…MC profiles of electron concentration and mean velocity in both high-µ and low-µ channels for different biasings demonstrate the velocity-modulation operation of the proposed transistor [7,8]. Concerning the dynamic performance of the 100 nm gate device, MC results show that the cut-off frequencies take values much lower than predicted [9] (the maximum value of f C estimated with the MC model is of the order of 200 GHz for a geometry similar to that of the experimental device [8]) because of the low g m associated to the VM behavior and, remarkably, to the high geometrical capacitance existing between the two gate electrodes when operating in DM, which is the main contribution to C IN [7,8]. To improve the frequency operation, the VMT geometry must be optimized for an enhanced g m and reduced C IN .…”

Section: Physical Modelmentioning

confidence: 75%

“…Thus, the drain current I D is modulated while keeping constant the total carrier density, and it is in principle possible to overcome the transit--time limit for high-frequency applications. However, the dynamic behavior of the VMT is not as exceptional as expected [9] due to the low values of the transconductance g m , and mainly due to the high capacitance be- * corresponding author; e-mail: bgvasallo@usal.es tween both gates C g1g2 [8]. In contrast, this device does not follow the traditional scaling rules for standard field effect transistors (FETs) and provides a high immunity to short-channel effects [8].…”

Section: Introductionmentioning

confidence: 95%

“…The progress of the DG-HEMT technology has allowed the design and fabrication of III-V velocity modulation transistors (VMTs) [7,8]. In VMTs [7][8][9][10][11][12][13][14][15], the conducting channel is divided into two regions, a high-mobility (high-µ) undoped channel and a low-µ channel obtained by compensated doping (N A = N D ), with two (top and bottom) gates controlling the electron density. Carriers are transferred between the two channels by changing the gate voltages (V G1 and V G2 ) in differential mode (DM), in which a potential ±V GDIFF /2 is added to a bias voltage V GOFF which adjusts the total channel electron concentration (V GDIFF = V G1 − V G2 ).…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo Analysis of the Dynamic Behavior οf InAlAs/InGaAs Velocity Modulation Transistors: A Geometrical Optimization

et al. 2011

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The influence of the geometry on the dynamic behavior of InAlAs/InGaAs velocity modulation transistors is analyzed by means of a Monte Carlo simulator in order to optimize the performance of this new type of transistor. In velocity modulation transistors, based on the topology of a double-gate high electron mobility transistor, the source and drain electrodes are connected by two channels with different mobilities, and electrons are transferred between both of them by changing the gate voltages in differential mode. Consequently, the drain current is modulated while keeping the total carrier density constant, thus in principle avoiding capacitance charging/ discharging delays. However, the low values taken by the transconductance, as well as the high capacitance between the two gates in differential-mode operation, lead to a deficient dynamic performance. This behavior can be geometrically optimized by increasing the mobility difference between the two channels, by increasing the channel width and, mainly, by reducing the gate length, with a higher immunity to short channel effects than the traditional architectures.

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“…We found that the band gap of the heterostructures was extended obviously. Heterostructure engineering is now widely practiced, producing the most efficient semiconductor lasers [9], highest-speed transistors [10], and novel quantum electronic devices [11]. If the nontransmission frequency range (PBG along the incident direction) of the constituents has a proper lineup, this can be essentially enlarged as desired by using different PCs to form photonic multiple heterostructures.…”

Section: Introductionmentioning

confidence: 99%