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.     

Passivated millimeter-wave silicon IMPATT diodes fabricated by ion implantation

Ion implantation has been combined with planar-mesa processing techniques to realize a passivated silicon IMPATT diode for millimeter-wavelength operation. A continuous-wave output power of 100 mW was obtained at 62 GHz from a fully passivated single-drift-region p⁺-n-n⁺structure.     

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.     

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.     

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.     

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.     

Liquid-nitrogen-cooled submillimetre-wave silicon IMPATT diodes

400 and 300 GHz c.w. oscillation characteristics for liquid-nitrogcn-cooled silicon IMPATT diodes are described. Output powers of 2.2 and 4.5 mW have been obtained at 412 and 295 GHz, respectively, and a highest oscillation frequency of 430 GHz observed.     

Influence of self-heating on the millimeter-wave and terahertz performance of MBE grown silicon IMPATT diodes

The influence of self-heating on the millimeter-wave (mm-wave) and terahertz (THz) performance of double-drift region (DDR) impact avalanche transit time (IMPATT) sources based on silicon (Si) has been investigated in this paper. The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited (NSVE) large-signal simulation technique developed by the authors, which is based on the quantum-corrected drift-diffusion (QCDD) model. Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed. Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques, which will be highly useful for optimizing the thermal design of the oscillators. Finally, the simulated results are found to be in close agreement with the experimentally measured data.     

Double-drift millimetre-wave IMPATT diodes prepared by epitaxial growth

The preparation of silicon double-drift millimetre-wave IMPATT diodes by the epitaxial growth of n- and p-type layers successively on n-type substrates is described. Carrier-concentration profiles comparable with those reported for double layers formed by ion implantation are obtained; a microwave output power of 560 mW with 11% efficiency has been achieved at 48 GHz.     

Design considerations of low-noise high-efficiency silicon IMPATT diodes

The noise and efficiency of p⁺-n1-n2-n⁺and n⁺-p1- p2-p⁺high-low silicon IMPATT diodes have been studied as a function of doping ratio n1/n2or p1/p2. In contrast to GaAs IMPATT diodes whose efficiency can be improved with some degradation of noise performance, both the efficiency and noise of Si IMPATT diodes can be improved. As an example, for a 6-GHz silicon n⁺-p1-p2-p⁺IMPATT structure with a doping ratio of 10, the efficiency is 21 percent and the incremental noise as compared to a uniformly doped structure is about -6 dB. These results indicate that silicon high-low structures can compete favorably with GaAs structures in both efficiency and noise performances.     

Design considerations of high-efficiency double-drift silicon IMPATT diodes

High-efficiency silicon double-drift IMPATT diodes with a low-high-low doping profile structure are proposed. Devices with efficiencies of 25 percent for 12 GHz, 24 percent for 18 GHz, and 19 percent for 50 GHz, are Predicted by numerical calculations.     

X-band silicon double-drift IMPATT diodes using multiple epitaxy

Silicon double-drift IMPATT diodes made by consecutive epitaxial deposition have been fabricated successfully. Output power in excess of 1.7 W with 10-percent efficiency was obtained at X band.     

Comparative studies of Si,GaAs, and InP millimeter-wave IMPATT diodes

High frequency limitations of Si, GaAs and InP IMPATT are investigated by concentrating on the effects of transient carrier transport and generation. A large-signal microscopic computer simulation is used to study the operating mechanisms in the 90, 140 and 220 GHz atmospheric windows. Inertial effects which can enhance or degrade the performance are identified first. The frequency and signal level dependence is then discussed in terms of intrinsic properties of materials.     

Interdiffusion of metallic contact layers on silicon IMPATT diodes

A comparative study, using Rutherford backscattering of He ions, of Ag/Pt/Cr and Au/Pt/Cr metallisations on silicon substrates has shown that significant interdiffusion takes place for Ag/Pt/Cr at temperatures around 350°C, resulting in the removal of the platinum barrier layer. No such effect takes place at the same temperature for Au/Pt/Cr. These results are consistent with the observed life-test performance of devices with these metallisations.     

Noise in epitaxial silicon bulk unipolar diodes

Silicon camel diodes with barrier heights in the range 0.46?0.94 eV were realised by means of low-pressure vapour phase epitaxy (LPVPE). These diodes show a conversion loss as low as 4.2 dB at 2 GHz and a noise figure of 4.8 dB.     

Semiquantitative treatment of transients in silicon epitaxial diodes

Three different types of p+?n?n+ device are considered, each having an effective centre-layer width much less than a minority-carrier diffusion length. Using simple arguments, the transient behaviour for `current switching? is analysed, and some basic parameters pertinent to modelling of such devices are derived.     

Multi-layer epitaxially grown silicon impatt diodes at millimeter-wave frequencies

Complementary (N⁺PP⁺) and double-drift (N⁺NPP⁺) silicon IMPATT diodes were prepared and investigated as oscillators in the millimeter-wave frequency region of 50 to 70 GHz. All the diodes were fabricated from multi-layer epitaxially grown silicon structures. A maximum CW output power level of 198 mW at 62.9 GHz and a maximum conversion efficiency of 7.3% have been measured for the complementary diodes. The double-drift IMPATT diodes have a maximum CW output power of 400 mW at 56.3 GHz and a maximum conversion efficiency of 8.5%.     

Effect of doping profile on avalanche noise of silicon IMPATT diodes

The open-circuit spectral noise-voltage density e2/?f of silicon IMPATT diodes with different punchthrough factors has been measured. A noise reduction has been obtained for diodes with punchthrough factors > 1. This is in agreement with theoretical curves calculated on the basis of the noise theory of Gummel and Blue.     

Lateral IMPATT diodes

Conventional IMPATT diodes are the highest-power microwave semiconductor devices, but they are difficult to couple light into, challenging to integrate into monolithic circuits, to incorporate a third terminal, or to series combine. The lateral IMPATT diode is proposed as a solution to these problems. This device is planar and features contact and drift regions that are all adjacent to the wafer surface. Two types of fabrication schemes are discussed and pulsed RF power results, up to 17.4 GHz, are demonstrated. This device structure promises to be well suited for microwave, millimeter-wave, and electrooptic integrated circuits in which maximum power is required     

Heterojunction IMPATT diodes

Heterojunction IMPATT diodes, which incorporate an abrupt GaAs/Al _0.3Ga_0.7As p/N heterojunction in place of the standard p/n junction, have shown a number of significant properties that represent a considerable technological advance. Ku-band experimental devices exhibit up to 2.0 dB higher power, superior DC characteristics, and 3-6 dB less phase noise content. These and other properties are examined in detail, and a first-order theory of operation is proposed