Hermann A. Haus

Bio: Hermann A. Haus is an academic researcher. The author has contributed to research in topics: Monolithic microwave integrated circuit & Negative resistance. The author has an hindex of 1, co-authored 2 publications receiving 459 citations.

Signal and Noise Properties of Gallium Arsenide Microwave Field-Effect-Transistors

Abstract: Publisher Summary This chapter examines the signal and noise properties of gallium arsenide (GaAs) microwave field-effect transistors (FET) High frequency gallium arsenide field-effect transistors (GaAs FETs) have demonstrated remarkably low noise figures and high power gains at microwave frequencies A practical microwave GaAs FET is usually fabricated by deposition or diffusion of source, gate, and drain contacts on the surface of an appropriately doped thin epitaxial n-type layer This layer, in turn, is grown on a semi-insulating wafer by either a vapor or liquid epitaxial technique The apparent minor role played by the negative resistance region in practical short-gate FETs suggests that radiofrequency instabilities due to this region, if they exist, occur at frequencies far above the normal frequency regime of microwave FETs The small-signal equivalent circuit of the FET, valid up to moderately high frequencies is elaborated It is found that noise in a microwave GaAs FET is produced both by sources intrinsic to the device and by thermal sources associated with the parasitic resistances

Modeling of noise parameters of MESFETs and MODFETs and their frequency and temperature dependence

Abstract: A simple noise model of a microwave MESFET (MODFET, HEMT, etc.) is described and verified at room and cryogenic temperatures. Closed-form expressions for the minimum noise temperature, the optimum generator impedance, the noise conductance, and the generator-impedance-minimizing noise measure are given in terms of the frequency, the elements of a FET equivalent circuit, and the equivalent temperatures of intrinsic gate resistance and drain conductance to be determined from noise measurements. These equivalent temperatures are demonstrated in the case of a Fujitsu FHR01FH MODFET to be independent of frequency in the frequency range in which 1/f noise is negligible. Thus, the model allows prediction of noise parameters for a broad frequency range from a single frequency noise parameter measurement. The relationships between this approach and other relevant studies are established. >

GaAs FET device and circuit simulation in SPICE

Abstract: We have developed a GaAs FET model suitable for SPICE Circuit simulations. The dc equations are accurate to about 1 percent of the maximum drain current. A simple but accurate interpolation formula for drain current as a function of gate-to-source voltage connects the square-law behavior just above pinchoff and the square-root law for larger values of the drain current. The ac equations, with charge-storage elements, describe the variation of the gate-to-source and gate-to-drain capacitances as the drain-to-source voltage approaches zero and when this voltage becomes negative. Under normal operating conditions the gate-to-source capacitance is much larger than the gate-to-drain capacitance. At zero drain-to-source voltage both capacitances are about equal. For negative drain-to-source voltages the original source acts like a drain and vice versa. Consequently the normally large gate-to-source capacitance becomes small and acts like a gate-to-drain capacitance. In order to model these effect it is necessary to realize that, contrary to conventional SPICE usage, there are no separate gate-to-source and gate-to-drain charges, but that there is only one gate Charge which is a function of gate-to-source and gate-to-drain voltages. The present treatment Of these capacitances permits simulations-in which the drain-to-source voltage reverses polarity, as occurs in pass-gate circuits.

A MESFET Model for Use in the Design of GaAs Integrated Circuits

Abstract: A MESFET model is presented that is suitable for use in conventional, time-domain circuit simulation programs. The parameters of the model are evaluated either from experimental data or from more detailed device analysis. The model is shown to be more complete than earlier models, which neglect transit-time and other effects. An integrated circuit (IC) design example is discussed.

Optimal noise figure of microwave GaAs MESFET's

Abstract: The optimal value of the minimum noise figure F o of GaAs MESFET's is expressed in terms of either representative equivalent circuit elements or geometrical and material parameters in simple analytical forms. These expressions are derived on a semiempirical basis. The predicted values of F o for sample GaAs MESFET's using these expressions are in good agreement with the measured values at microwave frequencies. The expressions are then applied to show design optimization for low-noise devices. This exercise indicates that shortening the gate length and minimizing the parasitic gate and source resistances are essential to lower F o . Moreover, a simple shortening of the gate length may not bring an improved F o unless the unit gate width is accordingly narrowed. The maximum value of the unit gate width is defined as the width above which the gate metallization resistance becomes greater than the source series resistance. Short-gate GaAs MESFET's with optimized designs promise a superior noise performance at microwave frequencies through K band. The predicted values of F o at 20 GHz, for example, for a half-micrometer gate device and a quarter-micrometer gate device are 3 and 2 dB, respectively. These devices could be fabricated with the current technology.

Determination of the basic device parameters of a GaAs MESFET

Abstract: This paper describes a new technique to determine the basic properties of the active channel of a gallium arsenide (GaAs) metal-semiconductor field effect transistor (mesfet). The effective gate length, channel thickness, and carrier concentration are determined from dc parameters. A precise method of measuring the dc parameters is also given. The new techniques are demonstrated using a wide variety of sample devices. It is also shown that microwave performance parameters, such as the maximum output power and minimum noise figure, are well predicted by dc parameters. Calculated values of the intrinsic and extrinsic dc parameters, using simple analytical expressions developed in terms of the geometrical and material parameters of a device, are shown to be in excellent agreement with their measured values. These expressions can be used as a basis for device design.