Electron Gas Field-effect Transistors Research Articles

Lateral Gate 2-D Electron Gas Field-Effect Transistor

We propose a new type of 2-D electron gas field-effect transistor (TEGFET) in which the top gate is replaced by two lateral gates (LGs), separated on each side of the conducting channel by a trench. In the etched trenches, air acts as a dielectric. The presence of LGs changes the channel potential, which in turn shapes the drain current. Thus, the drain current can be adjusted by the gates’ bias. This LG-TEGFET avoids the reliability problems due to the top gate: suppression of the electric field perpendicular to the 2DEG plane, reduction of the in-plane electric field, very low leakage current through the LGs, and no gate/semiconductor interface, which means reduced interface defects and reduced degradation due to heavy ions or high-energy particles and electromagnetic irradiation. Throughout the 1.5–300 K temperature range, the system exhibits very flat and stable saturations of the current–voltage characteristics, which are satisfactorily modified when a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{GS}}$</tex-math> </inline-formula> gate bias is applied to both LGs, or between the LGs. Our study suggests that this new TEGFET could be used in a wide range of applications involving III-V, III-V-N, and other devices.

Compensation for the Nonlinearity of the Drain–Gate I–V Characteristic in Field-Effect Transistors with a Gate Length of ~100 nm

The nonlinearity of the gate–drain current–voltage characteristics in classical Schottky transistors and two-dimensional electron gas field-effect transistors based on AlGaAs/InGaAs/GaAs and InGaAs/GaAs compounds is analyzed. The carrier velocity-overshoot effect in the transistor channel is analyzed for various doping profiles of the structures under study.

Компенсация нелинейности сток-затворной вольт-амперной характеристики в полевых транзисторах с длиной затвора &amp;#126;100 нм

Abstract The nonlinearity of the gate–drain current–voltage characteristics in classical Schottky transistors and two-dimensional electron gas field-effect transistors based on AlGaAs/InGaAs/GaAs and InGaAs/GaAs compounds is analyzed. The carrier velocity-overshoot effect in the transistor channel is analyzed for various doping profiles of the structures under study.

Magnetic‐TEGFET: Transistor Without a Gate

Low‐temperature current–voltage characteristics of n‐type GaAs/GaAlAs quantum wells delta‐doped in GaAs channel with Be acceptors are studied in the presence of a magnetic field. Negatively charged acceptor ions localize 2D conduction electrons by a combined effect of a quantum well and magnetic field parallel to the growth direction. In acceptor‐doped samples, the Hall electric field plays the role of the gate voltage. It is shown that at magnetic fields as weak as 1.5 T (or higher), the drain current reaches a constant value independent of the drain voltage. This phenomenon is due to the electron localization resulting in the decrease of conducting electron density in the crossed‐field configuration. The above special behavior of acceptor‐doped GaAs/GaAlAs heterostructures is exploited to realize a device called Magnetic‐TEGFET (Magnetic Two‐dimensional Electron Gas Field Effect Transistor) operating at low temperatures. The elimination of the gate in the studied transistor suppresses the gate‐to‐drain leakage current, which, in the standard TEGFETs, results in the electronic shot noise.

Magnetic two-dimensional field effect transistor

We study experimentally low-temperature current-voltage characteristics of n-type GaAs/GaAlAs modulation doped quantum wells under the influence of an external magnetic field. In particular, we use samples additionally doped in the well with Be acceptors. As showed previously, negatively charged acceptor ions can localize conduction electrons by a joint effect of a quantum well and an external magnetic field. It is found that, in the acceptor-doped samples, the Hall electric field resulting from the presence of magnetic field plays the role of the gate voltage. At sufficiently high magnetic fields, the drain current has a constant value independent of the drain voltage. It is argued that the above phenomenon is due to the electron localization with the resulting decrease of conducting electron density in the crossed-field configuration. We propose to exploit the observed unusual behaviour as a device called “magnetic two-dimensional electron gas field effect transistor” operating at low temperatures.

GaAs/AlGaAs field-effect transistor for tunable terahertz detection and spectroscopy with built-in signal modulation

We report gate-voltage-controlled signal modulation in terahertz (THz) spectroscopy with a GaAs/AlGaAs two-dimensional electron gas field-effect transistor. By utilizing Landau quantization with magnetic field and Fermi level tuning with the gate voltage, we observed that the amplitude of THz spectroscopic signals was largely modulated with the gate voltage and that the on-off ratio of the modulation reached over 40 dB. This result provides the possibility of a solid-state THz spectrometer with an active modulator.

선택적 분자선 에픽택시 방법에 의한 1D-2DEG 혼성 나노선 FET의 구현

High quality three-dimensional (3D) heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate to improve the efficiency of tarrier transport. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources (As2, As4) were varied to calibrate the selective area growth conditions and the 3D GaAs-AlGaAs heterostructures were fabricated into the ridge type and the V-groove type. Scanning micro-photoluminescence measurements and the following analysis revealed that the gradually (adiabatically) coupled 1D-2DEG (electron gas) field effect transistor (FET) system was successfully realized. These 3D-heterostructures are expected to be useful for the realization of high-performance mesoscopic electronic devices and circuits since it makes it possible to form direct ohmic contact onto the (quasi) 1D electron channel.

Wide-band transimpedance amplifiers using AlGaAs/In/sub x/Ga/sub 1-x/As pseudomorphic 2-DEG FET's

Monolithic wide-band amplifiers have been demonstrated using AlGaAs/In/sub x/Ga/sub 1-x/As/GaAs pseudomorphic two-dimensional electron-gas field-effect transistors. The amplifiers have yielded an 18.0 GHz bandwidth and a 41.8 dB/spl Omega/ transimpedance gain with a feedback resistance of 100 /spl Omega/. In addition, the dependence of In mole fraction for an In/sub x/Ga/sub 1-x/As channel layer on device and amplifier performance has been also investigated. The g/sub m/ and the f/sub T/ in a device, along with the bandwidth, the gain, and the noise performance in an amplifier, have improved as the In mole fraction is varied from 0 to 0.25.

Single electron effect transistor: Fabrication and observation

Single Electron Effect Transistors (SEET) based on the Coulomb blockade effect, have been fabricated in a TEGFET (Two-dimensional Electron Gas Field Effect Transistors) like configuration which involves a small 2D (Two dimensional) electron gas island obtained by Schottky gates. At low temperature these devices demonstrate clearly the periodic conductance oscillations when the electron number in the island increases or decreases monotonously, non-linear I-V relation when the system is selected at a blocked state, and linear I-V relation for a conducting state.

High electron density and mobility in single and double planar doped InGaAs/InAlAs heterojunctions on InP

We present results of a growth study concerning the electrical properties of lattice matched InAlGa/InGaAs single planar doped (SPD) and double planar doped (DPD) heterostructures grown on InP by molecular beam epitaxy (MBE). It is shown that room temperature electron mobilities (μ H) as high as 11000 cm 2/V·s at high sheet densities of 2.8x10 12 cm −2 can be obtained by optimizing the growth temperatures of each material in the SPD structure. High performance two-dimensional electron gas field effect transistors (TEGFET's) are demonstrated, with transconductances as high as 420 mS/mm at 1 μm gatelength and ƒ T's of 46 GHz at 0.7 μm gatelength. The DPD heterostructures further boost the n s values up to 6.2x10 12 cm -2 at μ H (300 K) = 6000 cm 2/ Vctdot; s.

Ga0.51In0.49P/GaxIn1-xAs lattice-matched (x=1) and strained (x=0.85) two-dimensional electron gas field-effect transistors

The authors report the fabrication of n-type GaInP/GaxIn1-xAs lattice-matched (x=1) and strained (x=0.85) two-dimensional gas field-effect transistors grown by low-pressure metallorganic chemical vapour deposition on GaAs semi-insulating substrates. The GaAs-GaInP devices demonstrate excellent operational performance at low temperature, due to the absence of deep traps in doped GaInP layers. The extrinsic transconductance is 163 mS mm-1 at 300 K and 213 mS mm-1 at 77 K. The threshold voltage of the devices biased in the dark at Vds=3 V was -3.34 V at 300 K and -3.38 at 77 K. Microwave measurements revealed cut-off frequencies fT of 17.8 GHz and fMAX of 23.5 GHz.

DC and RF characteristics of InAlAs/InGaAs dual-gate TEGFETs

DC and microwave measurements on 0.7 μm single-gate (SG) and dual-gate (DG) In0.52Al0.48As/In0.53Ga0.47As planar doped two-dimensional electron gas field-effect transistors (TEGFETs) are reported. The DG devices show a large increase of the gm to gD ratios, which are as high as 100 at gm = 380mS/mm, compared with 12 at 420mS/mm for the single gate (SG) devices on the same chip, as well as 6dB improvement in the RF power gain compared with their SG counterparts.

DC, small-signal, and noise modeling for two-dimensional electron gas field-effect transistors based on accurate charge-control characteristics

A practical model for DC, small-signal, and noise characteristics in two-dimensional electron gas field-effect transistors is discussed. The model includes accurate charge-control characteristics based on analytical functions relating carrier concentration to Fermi level. This model allows the influence of drain current, frequency, and device parameters on the noise figure (NF) to be studied. The theory explains the experimentally observed trend in NF behaviors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Accurate modeling for parasitic source resistance in two-dimensional electron gas field-effect transistors

An accurate two-layer model has been developed for parasitic source resistance in two-dimensional electron gas field-effect transistors (2DEGFETs). In this model, the 2DEG concentration-voltage and current density-voltage relations at the cap/barrier/2DEG junction are taken into account, based on the self-consistent charge control model and effective mass tunneling theory. Empirical 2DEG velocity field characteristics are also included. To show the feasibility of this method, the source resistance in conventional GaAs/AlGaAs 2DEGFETs was analyzed and the AlGaAs thickness dependence was discussed. For comparison, the lattice-matched GaInAs/AlInAs 2DEGFET and pseudomorphic GaInAs/AlGaAs 2DEGFET were examined. It was shown that introducing a highly doped cap layer leads to a drastic reduction in source resistance for pseudomorphic 2DEGFETs but has a very small effect for GaInAs/AlGaAs 2DEGFETs. >

Observation of subbands in the GaAlAs on two-dimensional electron gas field-effect transistor structures

We have measured the current-voltage characteristics and its derivatives on GaAs-GaAlAs field-effect transistor samples having a semitransparent Au-Schottky gate contact, varying the band structure by illumination. In these samples electrons tunnel from the two-dimensional electron gas through the GaAlAs into a Schottky gate. Sharp peaks are observed in dI/dV after illumination at liquid-helium temperature. Using a self-consistent model, we are able to explain these peaks by resonant tunneling via subband states in the GaAlAs.

Analysis of charge control in pseudomorphic two-dimensional electron gas field-effect transistors

An exact model for charge control in two-dimensional field-effect transistors (2DEGFETs) is discussed. The model is based on a first-principles theory, in which self-consistent quantum two-dimensional electron subbands and numerical solutions of Poisson's equation for band bending, space charge, and three-dimensional holes are included. The charge control in InGaAs/AlGaAs pseudomorphic 2DEGFETs is analyzed and compared with that in the GaAs/AlGaAs conventional 2DEGFET. It is shown that a quantum-well channel in the pseudomorphic 2DEGFET can achieve high carrier confinement as well as high carrier concentration. From the calculated gate capacitance-voltage behavior, a simple estimation for the device performance is obtained. The results indicate that the pseudomorphic 2DEGFET with a large conduction band discontinuity at the channel interface can improve transconductance-gate voltage characteristics, and thus maximum transconductance, and the cutoff frequency-gate voltage characteristics. >

Molecular-beam epitaxial growth and characterization of strained GaInAs/AlInAs and InAs/GaAs quantum well two-dimensional electron gas field-effect transistors

Defect free strained layer epitaxy opens possibilities for further improvement on the quantum well two-dimensional electron gas (TEG) structures grown using the GaInAs/AlInAs on InP materials system. Increased freedom with composition allows for optimizing certain properties of the structure, such as, the conduction edge discontinuity which controls the maximum sheet concentration (ns); and the electron effective mass which influences the speed of the structure. These enhancements can be made, respectively, by increasing the Al concentration in the AlInAs and/or by decreasing the Ga concentration in the GaInAs. The maximum amount of strain which can be incorporated into the unrelaxed material sets an upper limit on the compositional tolerances. The tolerances will be shown to be large for the AlInAs and the active TEG GaInAs region. The compositions are obtained using the intensity oscillations observed in the reflective high-energy electron diffraction (RHEED) specular beam during growth of GaAs, AlAs, and subsequently GaInAs and AlInAs on GaAs. X-ray rocking curves and photoluminescence (PL) are used to verify the calibrations for growths on InP. The dependency of the mobility on strain is shown. The maximum 300 K mobility obtained was 12 360 cm2/V s, with ns of 1.25×1012/cm2. The well thickness was 84 nm. The AlInAs and GaInAs were estimated to be +0.04 and +0.17 In mole fraction from lattice match, respectively. A mobility of 11 550 cm2/V s was obtained using a 34-nm well. InAs/GaAs superlattice quantum well TEG structures were grown and characterized. TEG field-effect transistors performance comparable to standard structures were obtained in preliminary layers. Exceptionally high Si doping levels roughly 20 times the maximum obtained with Al0.25Ga0.75As have been achieved with lattice matched AlInAs.

One-dimensional transport in quantum well wire-high electron mobility transistor

A novel one-dimensional electron gas field-effect transistor (FET) is proposed with the advantages of higher electron mobility and higher carrier concentration than conventional two-dimensional electron gas FET. The FET structure, device operation, and the low-field mobility of impurity scattering, which takes the screening effect into account, are discussed.

Noise modeling in submicrometer-gate two-dimensional electron-gas field-effect transistors

Noise modeling in TEGFET's which provides good results in agreement with the experimental findings is presented. The influence of the main technological parameters on the noise figure and associated gain is given for operating frequencies up to 60 GHz. A comparison between TEGFET's and MESFET's is carried out. A new method for calculating the noise and gain performances of FET's is then proposed.

Two-Dimensional Electron-Gas (2-Deg) Devices

Semiconductor structures giving two-dimensional electron-gas (2-DEG) are described and the advantageous properties of 2-DEG are enumerated.Principles of operation and structural details of the various 2-DEG (two-dimensional electron-gas) devices, TEGFET (tuned dimensional electron gas field effect transistor), MQW (multiple quantum well) lasers, DFWM (degenerate four wall mixer) and OBD (optical bistable device) are discussed, and the performance characteristics realized to-date are reviewed.