Light emission and burnout characteristics of GaAs power MESFET's

In order to obtain information on the field distributions and weak places of GaAs power MESFET's, the light emission and pulse burnout characteristics were investigated. Their dependence on the drain structure was also studied. The light emission occurs at the drain edge of the active region when the gate bias is zero volt, slightly changing its place depending on the drain structure. The drain edge of the epitaxial layer was also damaged by the pulse burnout experiments at zero gate bias. When the gate bias is increased, the light emission at the drain edge decreases rapidly until the gate Schottky breaks down and begins to give the light emission at the gate edge. The pulse burnout experiments suggest that the burnout initiates inside of the active or buffer epitaxial layer when the gate bias is near the pinchoff voltage.     

Reliability of the structure Au/Cr/Au-Ge/Ni/GaAs in lownoise dual gate GaAs FET

The first report based only on measurements using AES (Auger Electron Spectroscopy) profiles in GaAs FET with Al gate (ohmic contact Au-Ge/Ni/GaAs; Schottky contact Au/Cr/Al/GaAs) is presented.Six mm wide dual gate GaAs devices have been aged with and without DC bias conditions at different temperatures ranging from room temperature to 275°C. Other kinds of stresses have been made on these kind of devices like surge pulse test and endurance in humid ambiance.The different mechanisms which are involved in the degradation of the electrical characteristics are investigated and some correlation are established with the effects observed on the profiles of the elements constituting the ohmic contact and the gate contact.For each mechanism, the activation energy is given as well as the MTTF. By this way a prediction of what mechanism can cause the failure is obtained.Other use of the AES profiles can be made to find out all the parameters of the ohmic contact formation (layer thickness, annealing temperature).A new interpretation of the contact resistance increase is given by the support of AES profiles and fitting of experimental degradation with activation energy determination.     

Observation of high-frequency high-field instability inGaAs/InGaAs/AlGaAs DH-MODFETs at K band

The authors report the observation of high-field instability at room temperature with oscillation frequency as high as 24 GHz in GaAs/InGaAs/AlGaAs double-heterojunction-MODFETs (DH-MODFETs) of 1.2 μm gate length. Negative drain differential resistance was also observed in these devices under various forward gate biases. The nature of this instability is believed to be caused by the efficient removal of the real-space transferred hot two-dimensional electrons in the AlGaAs layer through the forward-biased Schottky gate. A tuned oscillator, with a fundamental oscillation frequency as high as 19.68 GHz, has also been demonstrated at a gate bias of 1.3 V     

Comparison for the carrier mobility between the Ⅲ-Ⅴ nitrides and AlGaAs/GaAs heterostructure field-effect transistors

Using the measured capacitance-voltage curves of Ni/Au Schottky contacts with different areas and the current-voltage characteristics for the AlGaAs/GaAs, AlGaN/AlN/GaN and In_0.18Al_0.82N/AlN/GaN heterostructure field-effect transistors (HFETs) at low drain-source voltage, the two-dimensional electron gas (2DEG) electron mobility for the prepared HFETs was calculated and analyzed. It was found that there is an obvious difference for the variation trend of the mobility curves between the Ⅲ-Ⅴ nitride HFETs and the AlGaAs/GaAs HFETs. In the Ⅲ-Ⅴ nitride HFETs, the variation trend for the curves of the 2DEG electron mobility with the gate bias is closely related to the ratio of the gate length to the drain-to-source distance. While the ratio of the gate length to the drain-to-source distance has no effect on the variation trend for the curves of the 2DEG electron mobility with the gate bias in the AlGaAs/GaAs HFETs. The reason is attributed to the polarization Coulomb field scattering in the Ⅲ-Ⅴ nitride HFETs.     

High temperature annealing behaviour of Schottky barriers on GaAs with gold and gold-gallium contacts

It is shown that unlike AuGaAs Schottky diodes, a Schottky barrier made on GaAs using an evaporated film of AuGa eutectic alloy does not degrade on heat treatment. It is shown that the presence of Ga in the top contact prevents micro-alloying to take place during heat treatment and thus prevents degradation of the diode behaviour.     

Gate controlled 2-DEG varactor for VCO applications in microwave circuits

A novel gate controlled Schottky diode varactor is introduced. The three-terminal varactor is a modulation-doped heterostructure of AlGaAs/GaAs with two Schottky contacts, similar to a metal–semiconductor–metal (MSM) diode. Schottky metal contacts are made to a two-dimensional electron gas (2-DEG). The third contact, the gate contact is formed from highly doped n⁺ GaAs material to allow an open optical window that can be used for optical gating and mixing. Structure capacitance is less than 1 PF and a change of more than 30% from the zero bias capacitance is observed with the applied gate voltage. On the basis of our quasi two-dimensional C–V model, the layer structure and device dimensions can be optimized and scaled to cover a wide range of operations in the microwave and millimeter wave regimes.     

New approach to the design and the fabrication of THz Schottkybarrier diodes

GaAs Schottky barrier diodes with near-ideal electrical and noise characteristics for mixing applications in the terahertz frequency range are described. The conventional formulas describing these characteristics are valid only in a limited forward bias range, corresponding to currents much smaller than the operating currents under submillimeter mixing conditions. Therefore, generalized analytical expressions for the I-V and C-V characteristics of the metal-semiconductor junction in the full bias range are given. A new numerical diode model is presented which takes into account not only the phenomena occurring at the junction, such as current dependent recombination and drift/diffusion velocities, but also the variations of electron mobility and electron temperature in the undepleted epi-layer. A diode fabrication process based on the electrolytic pulse etching of GaAs in combination with an in situ platinum plating for the formation of the Schottky contacts is described. Schottky barrier diodes with a diameter of 1 μm fabricated by this process have already shown excellent results in a 650-GHz waveguide mixer at room temperature     

Power gain and noise of InP and GaAs insulated gate microwave FETs

LPE GaAs and InP n-channel depletion mode insulated gate field effect transistors (MISFETs) having 4 μm gate lengths have been fabricated employing pyrolytic Si_xO_yN_z, pyrolytic SiO₂ and an anodic dielectric for gate insulation.The microwave power gain, noise figure, maximum output power and power-added efficiency were measured and compared to those parameters measured on GaAs Schottky barrier gate devices of identical geometry. The results show that, at least at the microwave frequencies measured, power gain and noise are essentially the same in the GaAs Schottky gate FET and anodic MISFET devices while the maximum output power of a typical InP MISFET was greater than that of a representative GaAs Schottky device.     

The GaAs MESFET as a Pulse Regenerator in the Gigabit per Second Range (Letters)

Regeneration and amplification of fast pulses in the 50-IPS range have been established using GaAs MESFET's under switching conditions. Sharpening factors, t/sub r in/ / t/sub r out/,of 3 and voltage amplification factors of 2 at 50 Omega have been achieved for output pulses up to 100 mA. The sharpening effect is caused mainly by the voltage-dependent gate capacitance which varies with the input pulse amplitude.     

A GaAs MESFET Self-Bias Mode Oscillator (Short Paper)

A self-bias mode oscillation in a GaAs MESFET, with the gate terminal kept open in a dc manner, has been analyzed by a large-signal MESFET circuit model. The circuit simulation demonstrates that the gate-source Schottky barrier becomes self-biased along with the microwave oscillation build-up and that a stable self-bias gate voltage is observed with a steady-state oscillation. A self-bias mode oscillator, operable with a single positive dc bias, is realized by rising microwave integrated circuit technology.     

Measurement of Richardson constant of GaAs Schottky barriers

The Richardson constants for near-ideal AuGaAs and AlGaAs Schottky diodes have been determined from an analysis of forward current-voltage characteristics. Measurement of capacitance-voltage characteristics at different temperatures shows that the barrier heights of the diodes have very similar temperature dependence for both Au and Al contacts. On taking into account the temperature dependence of the barrier height, the corrected value of the Richardson constant for AuGaAs diode is found to be very close to the predicted theoretical value. The corresponding value for AlGaAs diode is about a factor of five smaller which is explained on the basis of a thin interfacial layer between Al and GaAs.     

Hot-carrier luminescence in sub-quartermicrometer high-speed GaAsMESFET's

Hot-carrier luminescence in high-speed GaAs MESFET's with sub-quartermicrometer gate length was investigated at drain voltages high enough to permit breakdown. The spectral distribution of emitted radiation was analyzed in the energy range of 1.4-2.5 eV. GaAs MESFET's with a gate length of 0.18 μm yielded a prominent peak from the direct recombination across a GaAs bandgap of 1.43 eV. At energies above 1.65 eV, a broad continuous spectra with two peaks and a shoulder were detected. The two peaks coincide with the indirect recombination energies between holes in the Γ valley and electrons in the L or X valley. These peaks, however, were diminished at drain voltages as high as 7.5 V. It is suggested that the luminescence at energies above the bandgap mainly arises from the recombination of hot carriers, and the luminescence resulting from a phonon-assisted conduction to conduction-band transition is superimposed on it. The luminescence from the gate Schottky diode at reversed bias was also examined. There were no peaks from the direct recombination across the bandgap in the spectra. The light emission at the bandgap energy under the FET operation probably originates from the recombination of cold channel electrons and hot holes, which are generated by impact ionization and swept toward the source     

GaAs dual-gate Schottky-barrier FET's for microwave frequencies

The benefits inherent in the tetrode structure and the potential of GaAs are combined to realized a dual-gate FET with low noise and a wide dynamic range at microwave frequencies. A design theory of the dual-gate FET is constructed on the basis of the Lehovec-Zuleeg model for single-gate FET's. The theory has led to a new device structure having a second gate with a deeper pinchoff voltage than the first which shows improved gain and noise performance. Also derived is the importance of minimizing parasitic feedthrough due, for example, to packages. Samples were fabricated using n-type epitaxial GaAs. The first and second gates were Schottky barriers, 1.2 and 2.5 µm long. The improved channel structure was accomplished by reducing the thickness of the epitaxial layer under the first gate. Samples were mounted and characterized in specially designed small-size ceramic packages with a feedthrough capacitance of only 0.004 pF. The possibility of gain control by means of second gate bias over a wide bandwidth is demonstrated.     

Novel resonant tunneling transistor with high transconductance atroom temperature

A resonant tunneling transistor (RTT) utilizing a novel heterodimensional Schottky gate technology is described. The gate is formed by electroplating Pt/Au onto the side of an AlGaAs/GaAs double barrier structure. The gate voltage modulates the drain current by modulating the area of the quasi-two dimensional electron accumulation layer which forms above the source barrier under drain-source bias. Room temperature transistor characteristics included a peak current of 225 mA/mm and peak transconductance of 218 mS/mm. The ultrafine fabrication process is also discussed     

An electrically and optically gate-controlled Schottky/2DEGvaractor

A novel gate-controlled varactor is reported. The three-terminal varactor is a modulation-doped heterostructure of AlGaAs/GaAs with two Schottky contacts directly made to a two-dimensional electron gas (2DEG). The third, gate, contact is formed from highly doped n⁺ GaAs material to allow an open optical window that can be used for optical gating and mixing. Structure capacitance is less than 1 pF and a change of more than 30% from the zero bias capacitance is observed with the applied gate voltage. The capacitance also increases proportionally with applied light and inversely with the terminal voltage     

氮气氛下衬底负偏压预溅射对GaAs肖特基势垒性能的改善

本文研究了不同气氛下衬底负偏压预溅射对GaAs肖特基势垒特性的影响。我们发现,采用氮气氛下衬底负偏压预溅射新工艺能明显改善GaAs肖特基势垒特性:势垒高度增高,势垒电容减小和二极管反向击穿电压增大。这种新工艺对于GaAs肖特基势垒特性改善和GaAs MESFETs性能提高是一个非常有用的技术。     

LaB_6/GaAs肖特基势垒研究

用电子束蒸发LaB_6单晶的方法,制备了LaB_6/GsAs肖特基势垒,经800℃高温退火后,势垒高度为0.70eV,理想因子为1.15～1.2。用俄歇能谱观察到LaB_6/GaAs界面有良好的热稳定性,以LaB_6为栅得到了初步的全离子注入的MESFET特性。结果表明,LaB_6有希望用于GaAs集成电路。     

Inverted gate GaAs MESFET by epitaxial liftoff

A GaAs film deposited on metal by epitaxial liftoff can form a Schottky barrier. This film is used to make a 1 mu m gate length inverted gate GaAs metal-semiconductor field-effect transistor (MESFET) that can be pinched off by the inverted gate.<>     

High speed GaAs digital integrated circuit with clock frequency of 4.1 GHz

A maximum clock frequency of 4.1 GHz was obtained for a GaAs digital integrated circuit using deep recess normally-on GaAs MESFETs with 1.2 ?m long gate and interdigitated Schottky diodes. The Ti/Pt/Au gate electrode was made by a lift-off technique with conventional photolithography. The minimum propagation delay of a NAND/AND gate was estimated to be 100 ps/gate for a fan-out of 2 from the self-oscillation frequency of the master-slave flip-flops.     

Amorphous-Silicon gate GaAs FET's

Silicon-germanium-boron ternary amorphous alloy has been applied to GaAs FET as a gate contact material. A good Schottky contact with a barrier height as large as 0.94 V has been realized. Schottky-barrier gate GaAs FET's fabricated using the amorphous film as a gate contact layer exhibit excellent normally off FET characteristics of a large saturated drain curent, which has never been attained by conventional GaAs MESFET's.