Heat-sink temperature distribution of the annular solid-state microwave diode

It is shown that the heat-sink thermal conductance for an annular diode is more than twice that of a circular diode with equal area. Moreover, the annular diode radial temperature distribution at the diode/heat-sink interface is found to be considerably more uniform.     

A circuit mode chart for high-efficiency avalanche diode oscillators

A circuit mode chart for use with TRAPATT diode microwave oscillators is described. The chart relates the diode mean voltage and mean current levels to the parameters of the diode microwave waveforms. It consists of lines drawn in the diode `mean current-mean voltage' plane which define boundaries to an area in which the oscillator can operate. With the exception of a bias load line, these lines originate from consideration of the maximum and minimum values of the diode voltage waveform and from the properties of the two components, the trigger waveform, and the extraction waveform, into which the diode voltage may be resolved. It is shown how the chart takes account of waveform clipping at the breakdown voltage, frequency doubling, triggering, trapping, frequency shifts, an efficiency reduction effect, and the existence of a low-frequency cutoff. It is also shown how a dynamic characteristic, as well as a static breakdown characteristic may be incorporated on the chart.     

Shot-Noise in Resistive-Diode Mixers and the Attenuator Noise Model

The representation of a pumped exponential diode, operating as a mixer, by an equivalent Iossy network, is reexamined. It is shown that the model is correct provided the network has ports for all sideband frequencies at which (real) power flow can occur between the diode and its embedding. The temperature of the equivalent network is eta/2 times the physical temperature of the diode. The model is valid only if the series resistance and nonlinear capacitance of the diode are negligible. Expressions are derived for the input and output noise temperature and the noise-temperature ratio of ideal mixers. Some common beliefs concerning noise-figure and noise-temperature ratio are shown to be incorrect.     

Accurate Determination of Varactor Resistance at UHF and Its Relation to Parametric Amplifier Noise Temperature

A thorough investigation is made on the frequency-dependent properties of a varactor diode loss resistance at UHF. The variation of the losses with frequency in a varactor diode mounted cavity has been theoretically investigated, and it is shown that the previously reported inverse-squared frequency dependence of the varactor loss resistance can be attributed to the distributed cavity losses transformed across the varactor diode. A new measurement technique is introduced in which the circuit losses are first matched to the input line instead of the varactor loss resistance as an application of the relative impedance method. Measurements carried out with this technique for five different varactor diodes showed that the loss resistances of these diodes are not frequency dependent. It is also shown that the choice of the varactor diode capacitance plays an important role on the parametric amplifier noise temperature at UHF. In an experimental parametric amplifier the effect of varactor diode capacitance on the noise temperature has been demonstrated. It has been theoretically and experimentally shown that, generally, varactor diodes having higher capacitances result in better noise temperature at UHF.     

Heat transport and current crowding in IMPATT diodes

The current crowding due to the temperature dependence of avalanche breakdown is analyzed for the steady-state operation of an IMPATT diode mounted on a semi-infinite heat sink. The solution depends on a single new nondimensional number, the "Lambda" number, which we define here. This number can be determined from experimental data, and the current density and temperature distribution can then be determined from the results given in this paper. Experimental measurements of the I-V plot for a laboratory diode are shown to agree with the theoretical predictions. The theoretical model, which is based upon the assumption that the heat is entirely produced at the interface between the diode and the heat sink, is shown to agree with numerical results from a finite-difference program in which heat is introduced into a GaAs diode in a plane 0.5 µm above the interface. It is shown that electrical measurements of thermal resistance are related to an "effective" temperature which is about 15 percent below the temperature on the diode axis.     

Luminescence decay and injected carrier lifetime in the high injection region of AlGaAs lasers

Luminescence decays following short current pulse excitation of an antireflection coated AlGaAs laser diode have been measured. Using an optical gating technique, decays in the high injection region (simgthreshold density of uncoated lasers) were measured with a 100 ps time resolution. The observed luminescence decay is shown to be strongly affected by net gain in the active region. It is also shown that both monomolecular and bimolecular carrier recombination must be considered. A model has been developed that takes these effects into account and is shown to accurately describe steady-state and decay spontaneous emission intensities from laser diodes. A procedure is outlined for determining the necessary device and material parameters for interpreting laser diode characteristics.     

Reverse I-V characteristics in Au-GaAs Schottky diode in the presence of interfacial layer

The existence of an interfacial layer in an Au-GaAs Schottky diode may be revealed by measuring its I-V characteristics at very low reverse bias voltage. It is shown in this letter that a voltage dividing factor m can be used [see (2) of the text] to describe the effect of the interfacial layer on the I-V characteristics of the diode at low bias voltage.     

An Analysis of an Electronically Tunable N-GaAs Distributed Oscillator

The effective Schottky-barrier height of a contact to n-GaAs can be designed arbitraily by interposing a thin, highly doped layer between a metal and n-GaAs and by controlling the thickness optimally. An n-GaAs diode with a Schottky-barrier cathode exhibits various space-charge modes depending on the barrier height. A traveling dipole domain mode in an n-GaAs diode changes into a cathode trapped domain mode as the injection current at the cathode decreases. It has been shown that an n-GaAs diode, which operates in a cathode trapped domain mode, exhibits a negative conductance over a fairly wide frequency range. A super semiconductor. wide-band electronically tunable distributed oscillator can he achieved by inserting an n-GaAs diode with a suitably designed Schottky-barrier cathode between resonant microstriplines in place of conventional dielectric material. It has been shown that the frequency of the distributed oscillator would be electronically tunable over a fairly wide frequency range from 9 to 26 GHz.     

Scan performance of infinite arrays of microstrip patch elementsloaded with varactor diodes

The analysis and scanning characteristics of an infinite array of rectangular microstrip patches each loaded with a varactor diode is presented. The analysis is based on full-wave moment method theory and uses attachment modes to accurately model the current through the feed and the diode. The effect of the biased varactor diode on the scan performance is presented, and it is shown that the impedance mismatch caused by a scan blindness can be eliminated. Other characteristics are also given such as: the active element gain, the efficiency of each loaded microstrip element, and the level of cross polarization generated by the loading of the patch. The effect of the diode biasing level as well as the position of the diode on each radiating element on these scan characteristics is also considered     

Barrier height diminution in Schottky diodes due to electrostatic screening

Electrostatic screening in the metal contact of a Schottky (metal-semiconductor) diode is shown to influence the calculated electrical characteristics of the diode. A thin space-charge layer is formed at the surface of the metal contact by capacitively induced free charges, This results in a voltage dependent diminution of the barrier height of the diode that increases in magnitude with increasing semiconductor dielectric constant and carrier concentration. Predicted values of the barrier height diminution exceed those attributed to image forces or tunneling effects for materials with dielectric constants greater than about 20. In diodes using semiconducting ferroelectric or piezoelectric materials, an additional diminution of the barrier height results from free charges induced in the metal contact by a remanent polarization field or an externally applied mechanical stress. Current-voltage characteristics of a metal-semiconductor diode are shown to be significantly influenced by the electrostatic screening effect. A soft breakdown current as opposed to saturation current is predicted for reverse biases while an exponential forward current with an η coefficient exceeding unity is predicted for forward biases. Photoemission characteristics are also affected. A voltage-dependent diminution of the threshold energy for photoresponse is predicted. Capacitance-voltage characteristics, on the other hand, differ only slightly from those of an ideal Schottky diode except in the case of a ferroelectric diode where excessively large screening effects are possible.     

Broad-Band Characteristics of EHF IMPATT Diodes

Measurements have been made of the oscillator characteristics when a GaAs EHF double-drift IMPATT diode designed for a frequency of 35 GHz is operated over an extended frequency range from 33-50 GHz. The diode which was designed for 35 GHz has a broad-band capability which allows it to produce 2.15 W at 44.1 GHz. An analytic model is shown to predict accurately the observed results. The model indicates that the upper limit in frequency can be increased by reducing the diode area or the series resistance as well as by reducing the length of the drift region.     

Large Signal Analysis of a Parametric Harmonic Generator

Large signal analysis of a harmonic generator using a semiconductor diode reveals a larger possible efficiency than a similar small signal analysis. As higher harmonic numbers are reached, large signal analysis becomes increasingly more important in predicting the maximum conversion efficiency. It is shown that there exists an optimum value for the diode bias voltage and an optimum coupling of the load and generator to the diode, and that the diode operating voltage should almost drive the diode into conduction. An expression is derived for the maximum conversion efficiency for any harmonic, and it is shown that the conversion loss increases with increasing harmonic number, approximately 2.9 db per n for large harmonic numbers in a typical case.     

Voltage controlled minority carrier collection—the exponentially retrograded photodiode

The large retarding field in an exponentially retrograded photodiode is shown to significantly reduce the base-generated photocurrent at low reverse-bias voltages. Increasing the reverse voltage on the diode reduces the length over which this retarding field is effective, thereby increasing the Photo-Transmission Coefficient of the diode. From avalanche breakdown considerations, the largest ratio of change in photocurrent caused by this effect is shown to be only a function of the resistivity and bulk-lifetime in the base of the diode. This voltage-controlled collection effect is observable only in diodes with high background resistivity (i.e. silicon > 25 Ω cm.). It is theoretically possible to obtain voltage-controlled collection ratios of better than 50:1 in, typically, a 10 V junction swing.

Experimental results compare well with theoretical models.     

TRAPATT oscillations in a p-i-n avalanche diode

The characteristics of TRAPATT oscillations in a p-in diode are discussed and an approximate semi-analytical solution for the diode voltage waveform is derived when the diode current is a square wave. It is shown that a traveling avalanche zone is not necessary to generate a dense "trapped" plasma and that the boundary conditions prevent the trapped plasma from completely filling the depletion layer. Typical voltage waveforms and corresponding diode power, efficiency, and impedance at the fundamental and higher harmonics are presented. When the diode current is a square wave the diode does not necessarily exhibit a negative resistance at all higher harmonics. A computer program for TRAPATT oscillations in a p-i-n diode is described. Its running time is two or three orders of magnitude less than more exact time domain computer analyses. Typical results of diode power, dc to RF conversion efficiency, and required circuit impedances are presented for several different current waveforms which are composed of up to the seventh harmonic of a square wave and the first two harmonics of a half-wave sine wave. It is shown that high-efficiency oscillations are possible with diode currents composed of only the fundamental and one harmonic.     

A simple method for determining static parameters of large signal semiconductor diode and transistor models

A simple on-line interactive computing methodology for determining static parameters of large-signal semiconductor models is described. The procedure makes use of: (1) an automatic data collection scheme, (2) a single search, three-parameter optimization method for computing diode parameters, and (3) a partitioning scheme to separate the defining transistor equations into two single search, three-parameter problems which are solved by the diode optimization method described in (2).

The method is described by means of the CIRCUS diode and transistor models, and is compared experimentally with Sokal's method [1,2]. The new approach is shown to be superior.     

Classical infrared mixing with solid state diodes

It is shown that classical infrared diode mixing can compete with straight quantum detector diodes even if the available power gain of the diode mixer is as small as 10^?5–10^?6. To shed light on the diode mixer problem, the small signal diode detector problem is discussed, the effect of the series resistance r of the diode is dealt with and the time constants that may be operating in the device are evaluated. It is shown that Schottky barrier diodes operating in the diffusion mode are probably too slow, even though the response problem has not been solved exactly. Schottky barrier diodes operating in the thermionic mode are better; they can be understood in terms of a vacuum tube analogy, indicating that the characteristic time constant is the transit time of those electrons that just pass the barrier. Diodes operating in the tunneling mode have probably the fastest response, but an exact theory has not been developed. An interesting series resonance method is discussed that may lead to improved detector response near the resonance frequency.     

The resonant terahertz response of a slot diode with a two-dimensional electron channel

The terahertz response of a slot diode with a two-dimensional electron channel is calculated on the basis of the first principles of electromagnetism. It is shown that all characteristic electromagnetic lengths (scattering, absorption, and extinction lengths), as well as the impedance of the diode, exhibit resonances at plasmon excitation frequencies in the channel. The fundamental resonance behaves similarly to the current resonance in an RLC circuit. It has been concluded that, even at room temperature, a slot diode with a two-dimensional electron channel provides a resonant circuit at terahertz frequencies that couples effectively to external electromagnetic radiation with a loaded Q-factor exceeding unity. The diode resistance may be measured from contactless measurements of the characteristic electromagnetic lengths of the diode.     

High-power parallel-array IMPATT diodes

Fabrication of parallel arrays of silicon IMPATT diodes in which the arrays are formed in a single diode chip is described. The technique includes formation of an integral heatsink for the diode arrays during wafer processing. For a given total active device area, the use of a parallel array of smaller diodes, rather than one large diode, allows a significant reduction in thermal impedance and consequently larger power-dissipation capability. The contribution shown in the letter is the ease and economy with which parallel arrays on an integral heatsink can be fabricated and handled as a single entity. In a diode operated at 6.4 GHz, 3.5 W of c.w. output power has been achieved with a room-temperature copper heatsink and a junction temperature of about 280°C.     

Interface trap-enhanced gate-induced leakage current in MOSFET

Interface traps are shown to significantly affect the gate-induced drain-leakage current in a MOSFET or gated diode. The leakage current in a p⁺-gated diode can increase by two orders of magnitude when the interface trap density is increased from 10¹¹ to 10¹² cm^-2-eV^-1. The fact that thermal annealing at 300°C can eliminate both the generated interface traps and the excessive leakage current supports the close correlation between the two. The p⁺-gated diode is found to be more susceptible to this interface-trap related leakage current than the n⁺-device, which can be explained qualitatively by an interface-trap-assisted tunneling model     

Cross-modulation in ring diode modulators

Although intermodulation generation in ring diode medulators is the result of switching point interference and diode forward nonlinearity, cross-modulation is the result of the latter effect only. It is shown that the concept of variable trusconductance can be used to predict cross-modulation effects in ring diode modulators.