Schottky-Barrier Diodes for Submillimeter Heterodyne Detection

The fabrication and packaging techniques which were used to produce high-reliability mixer diodes for millimeter-wave satellite communications systems have been extended to produce Schottky-barrier mixer diodes for use in the submillimeter-wave region from 1 to 0.1 mm. The influence of material and circuit parameters on the performance of Schottky-barrier diodes as heterodyne detectors in the submillimeter-wave region has been considered. The semiconductor material parameters have been optimized and new packaging concepts have been investigated. A new diode package has been developed which incorporates both an integral stripline filter on 0.05-mm-thick quartz and a section of overmoded waveguide. The new package has the advantage of being replaceable in the mixer circuits, and yet it can provide a low-loss interface between the diode package and the mixer circuit. A new surface-oriented device has been developed in which the contact to the Schottky barrier is formed by photolithographic techniques onto the same surface as the ohmic contact. The surface-oriented devices exhibited heterodyne detection into the submillimeter region.     

Submillimeter Heterodyne Detection with Planar GaAs Schottky-Barrier Diodes

Planar surface-oriented Pt/GaAs Schottky-barrier diodes have been fabricated and used to detect signals at submillimeter wavelengths. Video detection has been observed up to frequencies as high as 890 GHz. Harmonic mixing between the ninth harmonic of a 74.21-GHz signal and the second harmonic of 333.95-GHz radiation has also been obtained.     

Cutoff Frequency of Submillimeter Schottky-Barrier Diodes

The traditional HF model of a bulk-type (nonepitaxial) Schottky-barrier diode is extended to include the influence of skin effect, carrier inertia, and displacement current. The parasitic cutoff frequency of the extended model is calculated for n-GaAs and n-Si and compared with that predicted by the traditional model. Below the plasma frequency, the two models are found to give similar results for n-Si. For n-GaAs, however, the extended model predicts a value of cutoff frequency only one-sixth that predicted by the traditional model. With both materials, operation near the plasma frequency is impractical since it would require unrealistically small contact dimensions. Above the plasma frequency, however, both materials display a broad frequency range where operation should again be feasible. For n-Si, the extended model predicts that operation above the plasma frequency can actually be achieved with Iarger contacts than is predicted on the basis of the traditional model.     

Conversion Loss in GaAs Schottky-Barrier Mixer Diodes

In this paper, the intrinsic conversion loss of GaAs Schottky-barrier mixer diodes is analyzed in light of a more accurate diode model. This analysis resolves the discrepancy between the predictions of an earlier intrinsic conversion loss model and expefimental results. In particular, it is shown that a) cryogenic cooling should not degrade the conversion loss, and b) the diode diameter can be smaller than previously predicted before conversion-loss degradation begins to occur, Evidence is also presented which indicates that mixer diodes must be pumped beyond flat-band if the minimum, possible conversion loss is to be obtained. A more complete model of the conversion loss, which includes the parasitic circuit elements, is discussed and found to be in agreement with the qualitative results of the intrinsic conversion-loss model.     

Transit-Time Effects in the Noise of Schottky-Barrier Diodes

Room-temperature noise measurements at 2.2, 12, and 97.5 GHz were performed on commercial silicon Schottky-barrier diodes and are shown to agree with the model presented in this work. This model is an extension of earlier work by van der Ziel on infrared detection in Schottky-barrier diodes. In the theoretical analysis, the electrons participating in the charge-transport process across the barrier are subdivided into four groups based on their initial velocity. The contribution of each group to the device conductance, susceptance, and current spectral intensity was incorporated including the effects of the transit time. By taking each of these effects into account, an accurate model which applies over a wide range of bias and frequency has been developed. Although the emphasis of this model has been on the high-frequency performance, the model also gives the correct results in the low-frequency limit.     

Interfacial Stress and Excess Noise in Schottky-Barrier Mixer Diodes

This paper presents evidence linking excess noise in submillimeter-wave Schottky-barrier mixer diodes to stress at the devices' GaAs-SiO/sub 2/ interface. At the periphery of the Schottky anodes, the SiO/sub 2/ film is discontinuous and the stress surpasses the GaAs yield stress, resulting in damage to the surrounding material. By modifying the device structure in three independent manners, the stress and damage at the diode periphery were either increased or decreased; in each case, the noise temperature increased or decreased accordingly.     

On Estimating and Canceling Parasitic Capacitance in Submillimeter-Wave Planar Schottky Diodes

The equivalent circuit model of a submillimeter planar diode is investigated. In particular, the parasitic finger to pad capacitance that shunts the diode junction severely degrades the performance of frequency multiplier. Therefore, precise estimation of its value is crucial to circuit design in the submillimeter wave range. In this letter, a parallel diode structure is analyzed, and symmetry is utilized to remove parasitic elements external to the finger loop. This analytical approach is verified through measurement on a 200 GHz planar diode circuit. To increase the diode junction capacitance modulation ratio, one possible solution is also suggested.      

Generation of Submillimeter-Wave Radiation with GaAs Tunnett Diodes and InP Gunn Devices in a Second or Higher Harmonic Mode

Efficient second-harmonic power extraction was demonstrated recently with GaAs tunnel injection transit-time (TUNNETT) diodes up to 235 GHz and with InP Gunn devices up to 325 GHz. This paper discusses the latest theoretical and experimental results from second-harmonic power extraction at submillimeter-wave frequencies and explores the potential of using power extraction at higher harmonic frequencies to generate continuous-wave radiation with significant power levels at frequencies above 325 GHz. Initial experimental results include output power levels of more than 50 μW at 356 GHz from a GaAs TUNNETT diode in a third-harmonic mode and at least 0.2–5 μW in the frequency range 400–560 GHz from InP Gunn devices in a third or higher harmonic mode. The spectral output of these submillimeter-wave sources was analyzed with a simple Fourier-transform terahertz spectrometer and, up to 426 GHz, with a spectrum analyzer and appropriate harmonic mixers. Initial experimental results from a GaAs/AlAs superlattice electronic device at D-band (110–170 GHz) and J-band (170–325 GHz) frequencies are also included.     

Backward Diodes for Low-level Millimeter-Wave Detection

Backward diodes (low peak current tunnel diodes) suitable for small-signal detection applications in the millimeter-wave region have been fabricated from n-type germanium. The diodes have the dimensions and geometry of point-contact diodes. For millimeter-wave signal levels below about - 20 dbm, the current sensitivity of these units is an order of magnitude greater than that of selected existing diodes for this frequency range. When employed as millimeter-wave frequency converters, the minimum conversion loss is comparable to that of conventional diodes, but the beating oscillator power requirements may be somewhat reduced. The diode noise factor at megacycle IF frequencies is comparable to that of conventional units, and in the low audio IF range it is expected to be markedly decreased. The fabrication of these diodes is described and their initial performance at selected frequencies from 11 Gc to 300 Gc is discussed.     

A memory-cell array with normally off-type Schottky-Barrier FET's

The potential of the metal-semiconductor field-effect transistor (MESFET) as a device for a dc-stable fixed-address memory-cell array is described. The implementation of dc-coupled circuits with `normally off' MESFET's having 1-/spl mu/m gate lengths yields several inherent advantages: high packing density, low power dissipation, low-power-delay time product, and low number of masking steps for transistors, diodes, and resistors. To demonstrate these advantages a fixed-address memory array with dc-stable cells has been chosen. The integrated cell area is 2.6 mil. For a supply voltage V/SUB s/=0.6 V, a standby power dissipation per cell of 5 /spl mu/W has been achieved. The cell switches within 4 ns. The differential sense current in the digit lines is /spl Delta/I/SUB s/=6 /spl mu/A.     

肖特基势垒红外焦平面阵列

介绍肖特基势垒IRCCD的结构和工作原理,制作工艺,目前国内外发展的状况和提高器件性能的各种措施.     

A 492 GHz Submillimeter-Wave Receiver

A 492 GHz submillimeter receiver was designed for application to the POrtable Submillimeter Telescope (POST). The receiver includes a Schottky diode mixer, a phase-locked Gunn oscillator at 82.3 GHz coupled with multipliers (×2×3), and low-noise amplifiers. In this paper, the system configuration and performance will be introduced.     

A VLSI-Suitable Schottky-Barrier CMOS Process

Trenched Schottky-barrier (TSB) contact PMOS devices for use in latchup-free CMOS are examined in detail, and compared to Schottky-contact PMOS. Measurements and simulations show that the TSB structure has significant advantages in gain and current leakage over the Schottky-contact structure, CMOS using TSB PMOS may be made unconditionally free of Iatchup. The tradeoffs involving PMOS source-drain implant dose are made explicit and correlated to Iatchup measurements.     

Analysis of Schottky-Barrier Millimetric Varactor Doublers

An analysis of abrupt-junction millimetric varactor doublers using Schottky diodes is performed and numerically implemented to evaluate conditions of maximum output power. This power level, the efficiency, and the circuit parameters have been derived as a function of the geometrical and physical parameters of the junction. Physical phenomena which allow the application of the model up to the plasma resonance frequency in epilayer are taken into account. Comparison of available experimental data with the theory developed is repotted.     

Schottky-Barrier Carbon Nanotube Field-Effect Transistor Modeling

The theoretical performance of carbon nanotube field-effect transistors (CNFETs) with Schottky barriers (SBs) is examined by means of a general ballistic model. A novel approach is used to treat the SBs at the metal-nanotube contacts as mesoscopic scatterers by modifying the distribution functions for carriers in the channel. Noticeable current reduction is observed compared to previous ballistic models without SBs. Evanescent-mode analysis is used to derive a scale length and the potential profile near the contacts for radially symmetric CNFET structures. Band-to-band tunneling current and ambipolar conduction are also treated. The effects of different device geometries and different nanotube chiralities on the drain-current are studied using this simple model. Quantum conductance degradation due to SBs is also observed     

RF Small-Signal Analysis of Schottky-Barrier p-MOSFET

This paper presents a detailed RF study for source/drain Schottky-barrier (SB) MOSFETs. Using on-wafer -parameters, high-frequency (HF) figures-of-merit (FoMs) and small-signal equivalent circuits (SSEC) are first extracted and discussed for a -gate-length SB MOSFET. Then, using ac simulations, HF FoM's sensitivity along SB height and underlap length variations are subsequently presented. The whole study provides, for SB MOSFETs, a deep understanding of key ac-element (transconductances and capacitances) behavior as well as process-parameter optimization to achieve the best HF FoMs.     

Nonlinear Analysis of the Schottky-Barrier Mixer Diode

The waveshape of the local-oscillator voltage component that exists across the nonlinear junction of a Shottky-barrier diode is a fundamental determinant of mixer performance. This waveshape significantly differs from that of the total local-oscillator voltage impressed across the diode terminals since it is influenced by parasitic, particularly spreading resistance and contact inductance, which exist in series with the junction. The junction-voltage waveshapes resulting from a 9.375-GHz sinusoidal local-oscillator generator voltage are computed for three common equivalent-circuit models of the diode. In the first model the diode is represented by a nonlinear conductance in series with a fixed spreading resistance. The second model includes the nonlinear capacitance associated with the junction, and the third additionally includes the contact inductance. In each case, the junction-voltage waveshape is significantly nonsinusoidal. It is shown that the contact inductance can induce a peak inverse junction voltage that greatly exceeds the peak voltage impressed across the diode terminals. This parasitic reactance thus can have an important bearing on the burnout properties of the mixer diode.     

Y Dielectric Waveguide for Millimeter- and Submillimeter-Wave

A new type of waveguide structure having Y cross section is presented and investigated theoretically. This waveguide is suitable for millimeter- and submillimeter-wave and facilitates supporting the waveguide with little field disturbance. Numerical results are presented for the dispersion characteristics, the transmission losses, and the power distributions using the generalized telegraphist's equations. The transmission characters of a triangular dielectric waveguide are also investigated as a special case.     

Threshold Voltage Variation in SOI Schottky-Barrier MOSFETs

The inhomogeneity of Schottky-barrier (SB) height Phi_B is found to strongly affect the threshold voltage V_th of SB-MOSFETs fabricated in ultrathin body silicon-on-insulator (SOI). The magnitude of this influence is dependent on gate oxide thickness t_OX and SOI body thickness; the contribution of inhomogeneity to the V_th variation becomes less pronounced with smaller t_OX and/or larger t_si . Moreover, an enhanced V_th variation is observed for devices with dopant segregation used for reduction of the effective Phi_B . Furthermore, a multigate structure is found to help suppress the V_th variation by improving carrier injection through reduction of its sensitivity to the Phi_B inhomogeneity. A new method for extraction of Phi_B from room temperature transfer characteristics is also presented.