High breakdown voltage AlAs/InGaAs quantum barrier varactor diodes

Data are presented on single quantum barrier AlAs/In/sub 0.53/Ga/sub 0.47/As varactor diodes intended as submillimetre wavelength frequency multipliers that exhibit extremely high breakdown voltage and excellent capacitance modulation characteristics. Record breakdown voltages as high as 12 V were achieved with a composite 50AA/50AA/50AA thick In/sub 0.52/Al/sub 0.48//AlAs/In/sub 0.52/Al/sub 0.48/As barrier sandwiched between 3000 AA(1.2*10/sup 17/ cm/sup -3/) In/sub 0.53/Ga/sub 0.47/As depletion regions.<>     

Theory for voltage dependent series resistance in silicon solar cells

A distributed parameter model has been proposed for p-n junction solar cells to account for the variation of series resistance due to the forward biasing of the p-n junction under external injection condition. The theoretical expression developed using this model predicts a coupling between base and emitter via depletion layer. This coupling becomes stronger with increasing bias and is found to be responsible for the observed decrease of series resistance with rising injection level. Numerical results of our theory are found to agree well with those obtained from experiments.     

Design considerations of hyperabrupt varactor diodes

This paper describes the design calculations and fabrication techniques used to produce hyperabrupt varactor diodes. The computation consists of determining, the doping profile, the capacitance as a function of applied voltage, the breakdown voltage, and the series resistance; allowance is made for the nonlinear variation of mobility with doping density. Fabrication of the retrograded region was accomplished by diffusion from a doped-oxide source. Two groups of diodes were fabricated. The first group had a breakdown voltage VBof 95 V at 1 µA, a capacitance ratio of 12 over a voltage range of 1 to 40 V (C_{P1}/C_{P40}=12), and a quality factorQof 60 at an operating level of 3 V and 100 MHz. The corresponding values for the second group were VB=45 V (C_{P1}/C_{P40}=4) andQ=210. The capacitance tracking capability of these diodes was found to be within 2 percent. These measurements showed excellent correlation with calculated results.     

Epitaxial layer induced series resistance and microwave properties of NNP Si X band impatt diodes

Following Gummel-Blue approach [1] [H.K. Gummel, J. L. Blue, IEEE Trans. Electron. Devices 14(1967) pp. 569-572.], the effect of undepleted epitaxial layers on the series resistance (R_s) as well as on its microwave properties of single drift region (n⁺np⁺) Si IMPATT diodes [2] [M. Mitra, M. Das, S. Kar, S.K. Roy, IEEE Trans. Electron. Devices 40(1993) pp. 1890-1893.] with flat doping profile with capacity 0.2PF at X band under experimental bias current of 25 mA and temperature 373 K have been studied. The computation for series resistance fits well with the device data for flat doping profile [2] [M. Mitra, M. Das, S. Kar, S.K. Roy, IEEE Trans. Electron. Devices 40(1993) pp. 1890-1893.]. The same study has also been simulated on its low-high-low (lhl) doping profile counterpart. The value of R_s increases approximately linearly with the increase of undepleted epi-layer thickness determined by the doping density for both flat and lhl structure. The value of R_s decreases remarkably as the doping profile changes from flat to lhl type.     

Characterization of IMPATT diodes at millimeter-wave frequencies

In order to evaluate the quality of a microwave device and to design a suitable circuit for it, the device must be characterized in terms of an equivalent circuit. At low microwave frequencies L through X bands, devices can be characterized in a relatively simple manner in conjunction with a coaxial transmission line network analyzer. At higher frequencies, such as millimeter-wave frequencies, however, the characterization must be carried out in a waveguide. This paper presents a technique for characterizing an IMPATT diode mounted in a waveguide and the associated circuit parasitics at millimeter-wave frequencies. The passive and active device parameters and the circuit parasitics, which have increased effects particularly at millimeter-wave frequencies, are evaluated by means of a computer-aided iterative curve-fitting method from the measured variation of the input impedance (VSWR) as a function of position of a movable short placed behind the device. The accuracy of the technique and the computer program are first checked by comparing the characteristics of anX-band IMPATT diode measured by the present technique and those measured by the network analyzer method. The characterization of a millimeter-wave IMPATT diode is then presented. A technique to achieve the stabilization required for the measurement of active parameters of the diode is also described. Comparison of the performance of an IMPATT diode amplifier calculated from the measured diode characteristics with the experimentally observed amplifier performance is then presented. It is shown that the device characterization technique can effectively be used for the analysis and design of a millimeter-wave circuit in which the device is used.     

Secondary-emission amplification at microwave frequencies

Two types of photomultipliers exhibiting flat base-band response to ∼4 Gc/s are described. One photomultiplier employs crossed electric and magnetic fields, the other is purely electrostatic. At present both devices consist of eight Cu-Be secondary emission stages and an internally situated, opaque-backed S-1 photocathode. Current gain exceeds 10⁵, and the transit time dispersion is less than7 times 10^{-11}s. Frequency response measurements have used heterodyning between the modes of the Zeeman-split Doppler profiles of a 6328 Å He-Ne laser, and also shot noise in the current from a steadily illuminated photocathode as sources of microwave modulated currents. Transient response measurements have been made using sub-nanosecond light pulses from phase-locked He-Ne and argon ion lasers, the results being consistent with the measured frequency response. A calculation of the frequency response to be expected fromnidentical stages of secondary emission when only the secondary electron emission velocities contribute to electron transit time differences, as is true of the geometries used in the experiments, gives results in agreement with experiment, assuming a value of 3 eV for the most probable secondary electron emission energy from BeO. This value is consistent with direct observations by others.     

Method of fabricating high-Q silicon varactor diodes

A new processing technique has been developed for the fabrication of high-Q and high-voltage varactor diodes. The process utilises ion implantation and laser annealing for heavily-doped p++ and n++ layers and epitaxial growth for low impurity concentrations. The technique provides good yield and repeatability, and it has allowed fabrication of varactor diodes which have breakdown voltages of 120 V and a Q as high as 600 at ?8 V bias and 50 MHz frequency.     

Measurement of series resistance in IMPATT diodes

A new method is given for determining the electrical series resistance of an IMPATT diode. The measurement is based on observation of the oscillation threshold bias current for a diode in a standard circuit. The method is applied to GaAs diodes near 40 GHz. The values obtained are used to quantitatively explain other performance characteristics of the diodes.     

A new resistance measurement technique applicable tohigh-temperature superconducting materials at microwave frequencies

A two-gap electrically floating resonant strip was used for surface resistance measurements of the high-temperature superconductor YBa₂Cu₃O_7-δ. The method is simple, has no electrical contact, operates at various resonant frequencies, and requires only a small sample. An analysis that allows for the accurate design of the strip dimensions to produce a desired resonant frequency was used. Experimental measurements on resonant frequencies in X- and Ku-band (8-18 GHz) agree well with the calculations. The method allows one to extract the normalized surface resistance of the sample from transmission coefficient measurements at the resonant frequency. These normalized values compare favorably to the Mattis-Baredeen theory taken in the local limit. The resonant strip in waveguide should have applications in high-temperature superconductive material characterization and in the development of waveguide superconductive filters     

The epHEMT gate at microwave frequencies

This paper examines the high-frequency behavior of the enhancement-mode pseudomorphic high electron-mobility transistor (epHEMT) gate. During this study, no bias was applied between the drain and source. Rather, the gate was forward biased with either the drain, source, or channel (drain and source connected together) grounded. While applying positive voltage V/sub g/ to the gate, one-port S-parameters were measured from 0.1 to 10 GHz and then converted to Z-parameters. Plotting the real part R of the impedance reveals two sharp peaks. The first peak occurs near the device threshold voltage for conduction in the InGaAs well. A second peak occurs at higher voltages where conduction begins to occur in the surface AlGaAs layer. An equivalent-circuit model is proposed to account for the epHEMT gate's high-frequency behavior and the proposed model is shown to be in good agreement with the experimental data.     

Cable shielding measurements at microwave frequencies

A matched triaxial device is developed and constructed to measure the transfer impedance of braided coaxial cables at microwave frequencies. Full-design principles of the device have been developed and given in detail in the paper. The device is particularly suited for shielding measurements at frequencies up to 3.5 GHz, for which no comparable technique exists. The performance of the device is fully evaluated both theoretically and by measurements. The accuracy of the device is studied by comparing the results against those obtained from the low-frequency International Electrotechnique Committee triple-coaxial apparatus, and using well-known theoretical models.     

`Source-pull? technique at microwave frequencies

A technique to produce a variable and controlled source impedance is described in order to evaluate the performance of microwave devices under source impedance variable conditions. The procedure for a systematic error correction is also presented.     

The silicon cryosar at microwave frequencies

Microwave and low-frequency measurements are reported onn^{+}-v-n^{+}silicon cryosars fabricated with narrow intrinsic region widths. The low-frequency measurements includeV-Idata with and without incident microwave power. The electric field required to cause impact ionization of the donors was found to be greater than 10⁵V/m. The microwave measurements include a demonstration of mixing, harmonic mixing, and harmonic generation. Small-signal impedance measurements as a function of bias are reported at 1.33 and 3.05 GHz, and the diode noise temperature was measured to be 16 000 or 3000 K depending on bias polarity. Mobile electron lifetime is 10^-10s.     

Silicon variable capacitance diodes with high voltage sensitivity by low temperature epitaxial growth

Low temperature epitaxial vapor growth of silicon has been successfully applied to the fabrication of variable capacitance diodes which have a hyperabrupt impurity distribution profile. These diodes exhibit a strong nonlinear behavior in capacitance voltage characteristics; for example, one of the diodes has the value of n as high as 15 in the differential capacitance formula:dC/C = -n dV/(V + Phi). It has been found that the capacitance voltage and current voltage characteristics agree well with those calculated from the impurity profile so that the diodes with a high voltage sensitivity and with a high quality factor can be designed and fabricated reproducibly by this technique, and used in all solid-state FM modulators and automatic gain control units in a microwave relay system transmitting multiplex telephone signals. The double breakdown phenomenon in the current voltage characteristic of some diodes was observed and proved to be the saturation effect of generation recombination currents.     

Measurement of surface impedance at microwave frequencies

A technique for measuring the surface impedance of a plane stratified media at microwave frequencies is given, and preliminary tests are made for a variety of situations ranging from capacitive impedances to surfaces, which display a purely inductive reactance. The technique utilises a modulated scatterer to measure the elliptically polarised electric field of a TM wave propagation over the surface.