High-performance millimeter-wave ion-implanted GaAs MESFETs

GaAs MESFETs (metal-epitaxial-semiconductor-field-effect transistors) with ion-implanted active channels have been fabricated on 3-in-diameter GaAs substrates which demonstrate device performance comparable with that of AlGaAs/InGaAs pseudomorphic HEMT (high-electron-mobility transistor) devices. Implanted MESFETs with 0.5-μm gate lengths exhibit an extrinsic transconductance of 350 mS/mm. From S-parameter measurements, a current-gain cutoff frequency f₁ of 48 GHz and a maximum-available-gain cutoff frequency f_max greater than 100 GHz are achieved. These results clearly demonstrate the suitability of ion-implanted MESFET technology for millimeter-wave discrete device, high-density digital, and monolithic microwave and millimeter-wave IC applications     

Double-drift-region ion-implanted millimeter-wave IMPATT diodes

A detailed experimental comparison between double-drift-region (DDR) and single-drift-region (SDR) millimeter-wave avalanche diodes is presented. For 50-GHz CW operation, DDR diodes have given a maximum of 1-W output power compared to 0.53 W for the SDR diodes, while maximum efficiencies of 14.2 percent for the DDR and 10.3 percent for the SDR diodes have been obtained. These results are in agreement with the theory of Scharfetter et al. [1] for DDR IMPATT diodes. Both the DDR and SDR diode measurements were made on room temperature, metal heat sinks. The DDR diodes were shown to operate at significantly lower junction temperatures for the same value of output power, indicating a potential reliability advantage. Ion implantation was used to make the p drift region of the p⁺p-n-n⁺50-GHz DDR devices. Otherwise the fabrication (which includes diffusion and epitaxial technologies) and the microwave measurement methods were identical for both types of diodes. Capacitance measurements were compared with calculations to determine the desired doping concentrations for frequencies from 43 to 110 GHz. Experimental results for the higher frequency millimeter-wave region have been obtained on DDR structures with both p and n drift regions implanted. At 92 GHz an output power of 0.18 W and an efficiency of 7.4 percent have been obtained.     

Properties of millimeter-wave IMPATT diodes

A study of the effect of the doping profile on the properties of IMPATT devices has been carried out and the results of a small-signal analysis for different ram-wave Si IMPATT-diode structures are presented. Properties of single-drift abrupt-junction diodes of both Si complementary structures with different punch-through factors (PTF) are described and compared to those of symmetrical and asymmetrical double-drift diode structures. Since the initiation of the TRAPATT mode may be related to the IMPATT performance, these results should also be useful in assessing the effects of the doping profile on TRAPATT initiation.     

Sb-heterostructure interband backward diodes

Backward diodes are a version of Esaki tunnel diodes that are useful for mixing and detection. Ge backward diodes in particular have been used as temperature insensitive, zero bias square law detectors, capable of translating low level RF power into DC voltage or current with extreme linearity and low noise. However, Ge diodes are difficult to reproducibly manufacture and are physically fragile. Here we demonstrate specially designed Sb-heterostructure-based backward diodes grown by molecular beam epitaxy. These diodes have superior figures of merit compared to Ge diodes, especially the current density and junction resistance, and are reproducible and physically rugged. In addition, the flexibility of MBE growth allows easy tailoring of the layer structure to maximize the desired figure of merit for a given application     

High-performance quantum-dot superluminescent diodes

By inclining the injection stripe of a multiple layer stacked self-assembled InAs quantum dot (SAQD) laser diode structure of 6/spl deg/ with respect to the facets, high-power and broad-band superluminescent diodes (SLDs) have been fabricated. It indicates that high-performance SLD could be easily realized by using SAQD as the active region.     

Fast pulsed gallium arsenide heterostructure diodes

Switching of properties of gallium arsenide heterostructure diodes has been studied. It is shown that use of a graded-gap base region or a wide-gap “wall” (abrupt heterojunction) enables control over the distribution of injected carriers and their accumulation near the p-n junction, which leads to a faster reverse-voltage recovery (60–70 ps). Structures are considered in which an impurity gradient is used, together with the gradient of the energy gap, in order to make the working voltage higher.     

High-performance thin-film encapsulation for organic light-emitting diodes

Organic light-emitting diodes degrade rapidly by means of local cathode oxidation when exposed to the ambient atmosphere, resulting in visible non-emissive areas called black spots. High performance inorganic based encapsulations are required to protect the OLED. We have applied a hybrid thin-film encapsulation stack consisting of two inorganic barrier layers of silicon nitride deposited at low temperature with an organic layer in between. The resulting water permeation mechanism into the OLED is solely by means of lateral pinhole-to-pinhole transport. With the application of CaO nanoparticles in the organic layer the lateral water transport rate is reduced and we show that black spot formation in 8 cm² OLEDs is delayed by 6000 h at accelerated climate conditions of 60°C/90% relative humidity. This is estimated to correspond to 20 years at ambient conditions.     

Interband tunneling in heterostructure tunnel diodes

A particular type of tunnel diode, incorporating a wideband tunnel barrier, is studied. Simple analytic expressions are developed for estimating the tunneling coefficients to guide and optimize the design of heterostructure interband tunnel devices. The interband tunneling in such heterostructure tunnel diodes is modeled by a two-band Schrodinger equation. For a certain family of InGaAs/InA/GaAs p-n junction tunnel diodes, the interband transmission coefficients are calculated. The estimated peak currents are shown to compare very favorably with experimental results     

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.     

Multilayer vapor-phase epitaxial silicon millimeter-wave IMPATT diodes

A new procedure has been developed for fabricating small-area silicon avalanche diodes directly on a plated copper heat sink. The process incorporates multilayer vapor-phase epitaxially grown silicon and a preferential electrochemical etching technique to fabricate thin uniform silicon films; 6 µ thick films on 2-cm diameter wafers have been obtained reproducibly with little difficulty. Inverted mesa diodes 30-40 µ in diameter have been formed by etching through the unmasked area of the thinned silicon wafer. Implementation of this technology has resulted in single drift region p⁺-n-n⁺diodes that generate over ¼ W CW power with 6-percent efficiency at 60 GHz.     

High-performance, high-reliability buried heterostructure lasers byMOVPE

The authors report the first highly reliable all-MOVPE BH lasers. These devices have extremely low threshold currents (≃10 mA) and show excellent uniformity of device characteristics. Data are presented to show the high yields achieved and demonstrate the very low degradation rates achieved under accelerated aging     

InGaAs zero bias backward diodes for millimeter wave directdetection

Backward diodes are a version of Esaki tunnel diodes that are useful for mixing and detection. Ge backward diodes in particular have been used as temperature insensitive, zero bias square law detectors, capable of translating input RF power into dc voltage or current with extreme linearity and low noise. However, Ge diodes are difficult to reproducibly manufacture and are physically fragile. Here we demonstrate specially designed InGaAs-based backward diodes grown by molecular beam epitaxy. These diodes have superior figures of merit compared to Ge diodes, are reproducible and physically rugged, and are compatible with InGaAs high electron mobility transistor (HEMT) low noise amplifier fabrication technology. In addition, the flexibility of MBE growth allows easy tailoring of the layer structure to maximize the desired figure of merit for a given application     

HgCdTe/CdTe heterostructure diodes and mosaics

This paper discusses the results of a study of the properties of HgCdTe/CdTe heterostructure diodes and mosaics. In this study, p-type HgCdTe epi-layers on the order of 20 µm were grown on CdTe substrates by a liquid-phase epitaxial (LPE) technique. These layers normally had a carrier concentration of 5 × 10¹⁶/cm³and a mobility of 400 cm²/V . s at 77 K. The n⁺-p junction was formed by boron ion implantation, and standard photolithographic techniques were used for the device fabrication. The diodes with no antireflection coating had a typical quantum efficiency of 40 percent. The 1/fnoise knee was on the order of 10 Hz at zero bias. Surface leakage seemed to be the dominant component for diodes at temperatures less than 77 K. From mosaic studies, it was found that the spectral spread was less than ±0.3 µm for an area as large as 12 × 20 mm. The study indicates that LPE offers a viable technique for producing high-quality HgCdTe epi-layers on CdTe.     

Optimum transit angles of millimeter-wave Si IMPATT diodes

Optimum transit angles for maximum output power in the millimeter-wave IMPATT diodes are calculated analytically by considering the carrier diffusion process through the space-charge region. It is found that the optimum transit angle decreases, as the space-charge layer width reduces. The theoretical results show satisfactory agreement with the previously published experimental results for Si p⁺-n-n⁺abrupt junction diodes.     

Performance of P-type epitaxial silicon millimeter-wave IMPATT diodes

A series of p-type IMPATT diodes (p⁺pn⁺) have been fabricated from epitaxially grown silicon for operation as oscillators at Ka-band frequencies. A maximum CW output power level of 700 mW at 29.6 GHz, a maximum conversion efficiency of 10.9 percent, and a minimum FM noise parameter, M, of 25 dB have been measured on this series of p-type diodes. A diode oscillating in a variable height radial disk cavity was frequency tuned from 27.5 to 40 GHz, covering the entire Ka-band, with a 1.4 dB power variation over the tuning range. The minimum CW output power of this tunable oscillator was 360 mW at 6.5 percent efficiency.     

High sensitivity Si-based backward diodes for zero-biased square-law detection and the effect of post-growth annealing on performance

High-sensitivity Si-based backward diodes were realized that are monolithically integratable with transistor circuitry. Potential applications include large area focal plane arrays. The Si-based backward diodes exhibit a high zero-biased curvature coefficient, /spl gamma/, of 31 V/sup -1/ and a low zero biased junction capacitance, C/sub j/, of 9 fF//spl mu/m/sup 2/, all at room temperature. The predicted low frequency voltage sensitivity, /spl beta//sub V/, for a 50 /spl Omega/ source is 3100 V/W. The high sensitivity, low junction capacitance, and Si/SiGe heterojunction bipolar transistor compatibility of the Si-based backward diodes make them very attractive for zero-bias square-law detector applications.     

High-performance 450-GHz GaAs-based heterostructure barrier varactor tripler

In this letter, we report on the record performance of GaAs-based heterostructure barrier varactors (HBVs) in tripler circuits. Both fabrication technique of planar Al/sub 0.7/Ga/sub 0.3/As/GaAs heterostructure barrier varactors (HBVs) and measurements of a corresponding tripler circuit are presented. Planar transmission lines on a thin dielectric membrane and flip-chip technique without air bridges provide reduced parasitic losses and, hence, higher tripler efficiency. Frequency tripler measurements have shown more than 1 mW at 450 GHz.