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.     

Generalized small-signal analysis of avalanche transit-time diodes

The one-dimensional small-signal analysis of avalanche transit-time diodes with distributed multiplication is reduced to the concept of two layers in cascade, each having a constant ionization rate. The interface is located in the distinguished neutral plane of equal direct electron and hole currents. In this configuration the small-signal problem is characterized by two parameters : namely the location of the neutral plane in the depletion layer and a quantity combining the ionization-rate field dependence and the total direct current density. Normalized admittance diagrams and small-signal growth rates are given which show the relative importance of the low-transit-angle mode where the frequency is smaller than the avalanche resonance frequency and the π mode extending almost to 2π for large current densities. Through a transformation the results are applicable to Read type, abrupt and uniform junctions of Si, Ge, and GaAs avalanche diodes.     

Large-signal theory for rectangular-voltage operation of a uniform avalanche zone in IMPATT diodes

Explicit solutions are derived for the currents in a lightly doped high-field zone of an IMPATT diode subject to constant E field avalanche. Resulting particle-current waveforms, diode impedances and r.f. powers are calculated for Si and GaAs with the avalanche period followed by a sudden transition to a low-voltage carrier-extraction period. It is concluded that the addition of a drift zone will only ease impedance matching and enhance efficiency when differences of either ionisation rates or drift velocities between electrons and holes exist.     

Accurate calculation of small-signal growth rates in avalanche diodes

The small-signal oscillation frequency and growth rate is calculated for an avalanche diode having a general doping profile, allowing for accurate drift velocity and ionisation rate. The analysis includes the case of a typical microwave load connected to the diode. A connection is found between this accurate growth rate and a properly defined Q factor for the whole circuit.     

Effects of tunneling on high-efficiency IMPATT avalanche diodes

A theoretical and experimental study is presented of the effects of tunnel injection on high-efficiency IMPATT avalanche diodes characterized by a high low-doping profile. Some characteristics usually observed in such high-efficiency IMPATT oscillators are explained, taking into account the effects of tunneling.     

Effect of carrier diffusion on the small-signal behavior of IMPATT diodes

An approach to the detailed computer simulation of dc and small-signal IMPATT behavior is described in which allowance is made for carrier-diffusion effects. Results are presented for a variety of structures in Si and GaAs, including high-efficiency structures using the latter material. The results from the simulation are also compared with the predictions of a quasi-static theory for a particular case, and good general agreement is observed.     

Delayed secondary avalanche effects in millimeter wave GaAs IMPATT diodes

A simulation of the large signal operation of GaAs millimeter wave IMPATTs shows that a high peak current density of electrons (often in excess of 25KA/cm²) will lead to a delayed secondary avalanche (DSA) in the drift zone. These DSA effects have been simulated and correlated with experimental observations and are a determining factor in achieving high power and high efficiency in GaAs IMPATTs at 40 GHz and above.     

Multiplication noise in uniform avalanche diodes

A general expression is derived from which the spectral density of the noise generated in a uniformly multiplying p-n junction can be calculated for any distribution of injected carriers. The analysis is limited to the white noise part of the noise spectrum only, and to diodes having large potential drops across the multiplying region of the depletion layer. It is shown for the special case in whichbeta = kalpha, wherekis a constant and α and β are the ionization coefficients of electrons and holes, respectively, that the noise spectral density is given by2eI_{in}M^{3}[1 + (frac{1 - k}{k})(frac{M - 1}{M})^{2}]where M is the current multiplication factor and Iinthe injected current, if the only carriers injected into the depletion layer are holes, and by2eI_{in}M^{3}[1 - (1 - k)(frac{M - 1}{M})^{2}]if the only injected carriers are electrons. An expression is also derived for the noise power which will be delivered to an external load for the limitM rightarrow infin.     

Low-frequency noise of ion-implanted double-drift IMPATT diodes

The low-frequency open circuit noise spectral density S(f) of an ion-implanted 60-GHz double-drift-region IMPATT diode was measured as a function of the dc avalanche current I0. Over an intermediate current range the noise follows an S(f)=a²VB0²/I0relationship where VB0is the reverse breakdown voltage and a²≃4.5 × 10^-20A/Hz.     

Small-signal noise measure of avalanche diodes

A study of small-signal noise measure of avalanche diodes is useful for establishing a reference for large-signal noise theories as well as to determine conditions for low noise operation in low power applications. Such a study depending largely on numerical calculations was presented by Haus et al. Similar results are derived by analytic techniques through the use of a second-order approximation for the avalanche current accounting for transport delay of the carriers in the avalanche region.A uniformly avalanching PIN diode is studied to derive the properties of the avalanche region. In the lossless case the noise measure has a minimum for a carrier transit angle of approximately 2π, while it is inversely proportional to frequency squared for smaller transit angles. Operation close to the avalanche frequency is favorable in a practical case because of parasitic series resistance.The effects of a drift region is included to obtain reasonable modeling of practical avalanche diodes. In the lossless case the impedance transformation and space-charge smoothing in the drift region cause a strong modulation of the noise measure with minima for drift transit angles π < θ_d < 2π and 3π < θ_d < 4π. The noise measure decreases for increasing avalanche widths. Series resistance limits the practical upper drift angle to approximately 1.2π due to the decrease of the negative resistance with frequency.Similar calculations have been carried out for double-drift-region diodes, and show that these in general are noisier than the corresponding single-drift structures in the small-signal limit.     

1f noise in uniform avalanche diodes

The $\text{1}\text{f}$ noise in small silicon diodes with uniform breakdown is low in amplitude and independent of current and temperature. The noise is not explained by existing bulk $\text{1}\text{f}$ noise models. A type of burst noise is observed on diodes smaller than 6 μm.     

A series connection of IMPATT diodes

A microwave oscillator using a series combination of three packaged IMPATT diodes has been successfully operated. Since the series combination increases the power output of IMPATT oscillators without decreasing the impedance level, the 1/f²limitation of the power-impedance product for IMPATT diodes can be avoided. This type of series combination is suited for use at millimeter-wave frequencies.     

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     

Double-velocity IMPATT diodes

A new IMPATT diode structure is proposed. The device incorporates a heterojunction between materials having different electric field saturated carrier velocities. Analysis shows that such a diode can have significantly higher dc-to-microwave-power conversion efficiencies than conventional Read IMPATT diodes.     

A comparative study of noise properties of Si IMPATT diodes operating at 80 GHz

The oscillator-noise properties of three kinds of Si IMPATT diodes operating at 80 GHz are measured. A DDR type of diode is superior in FM noise measure to the other two SDR types, one of which operates in the fundamental frequency mode and the other in the second harmonic frequency mode.     

Current tuning and the concept of avalanche resonance in IMPATT diodes under large signal operating conditions

The concept of current tuning, i.e. the increase of optimum frequency with current density, is well-known in IMPATT diodes. An explanation of the phenomenon by postulating an avalanche resonance frequency was derived by Gilden and Hines from small-signal theory. Difficulties arise however when the small-signal theory is extrapolated to large signal operation. This paper provides a coherent explanation of the zero conductance and susceptance frequencies (which can be related to the avalanche resonance concept in an idealised diode model) and current tuning by utilizing a modified approach to Gilden and Hines theory which can then be extrapolated to large signal behaviour. Large signal computer simulation of diodes is used to verify the conclusions on the zero conductance and susceptance frequencies and current tuning under large signal conditions with varying frequency, drive level and current density. By examining the waveforms of the simulated diodes the cause of the zero conductance frequency (avalanche resonance at small signal levels) and current tuning can be shown to be due to the perturbation of the avalanche region electric field by the space charge of the drifting charge bunch.