In a distributed IMPATT structure, power is coupled out through a side contact. That is, in previously proposed distributed IMPATT structures the gain medium (the active region of the IMPATT) operates as a transmission line. The prior art has attempted to couple output power from the gain medium through an end contact, i.e. through a contact which intercepts the primary direction of energy propagation of the active medium. In the present invention, a side contact extends along the whole active region in a direction which is parallel to the principal direction of propagation of the energy in the active medium. Thus, the side contact plus the active region together can be considered as a single transmission line. The present invention can be configured as an oscillator, amplifier, phase shifter, or attenuator. When configured as an oscillator, multiple short active regions can be sequentially coupled to a single long microstrip, which serves as the side contact for each of the active regions. This very simple power combining scheme provides extremely high power at millimeter wave frequencies.

Distributed IMPATT structure

Influence of heat-treatment on the morphological and electrical properties of the GaAs epilayer-substrate interface

In a metal-semiconductor junction the difference between the work function of the metal φm and the electron affinity χs of an n type semiconductor, Fig. 2.1 (a), determines the barrier height (φm − χs) for the simple model shown on Fig. 2.1(b). This barrier forms by equalization of the Fermi levels across the junction due to the movement of electrons from the semiconductor to the metal interface. The barrier in the semiconductor itself is qV D = φm − φs and the junction conducts in the forward direction by movement of electrons over this barrier when the n type semiconductor is made negative with respect to the metal. If the work function of the metal is less than that of the n type semiconductor the barrier does not exist in this model and the junction is ohmic. However, if the semiconductor is p type and φ m < φ s then, as in Fig. 2.1(c) and (d), a rectifying junction is expected, and forward current flows when the semiconductor is positively biased with respect to the metal.

Metal-Semiconductor Schottky-Barrier Diodes

Monolithisch integrierte Schaltungen auf GaAs haben in den Jahren seit 1980 einen auserst raschen Aufschwung genommen. Dieses Kapitel kann daher nur einen kurzen uberblick uber den bis jetzt erreichten Stand (1988) bei analogen und digitalen Schaltungen geben. Ausfuhrliche Informationen uber GaAs-IS sowie uber neueste Entwicklungen (optoelektronische integrierte Schaltungen, Schaltungen auf anderen III-V-Halbleitern als GaAs oder auf Schichtfolgen) sind z.B. in Tagungsbanden zu finden: 


GaAs IC Symposium (jahrlich seit 1979),


International Solid-State Circuits Conference,


Symposium on GaAs and related compounds.

Ausblick: Monolithisch integrierte Schaltungen auf GaAs

Diodes provide many circuit functions (e. g., detection of signals, modulation of carrier frequencies with signal frequencies and subsequent demodulation) at high frequencies. Diodes are also used as RF switches and as harmonic generators for efficient frequency multiplication. The variable capacitance feature of varactor diodes is used in voltage-controlled oscillators for tuning purposes and in parametric amplifier circuits. Tunnel diodes also have similar uses.

Microwave Applications of Diodes, Varactors and Tunnel Diodes

A new concept for integrated planar Schottky-diodes has been developed. It meets the two important requirements in the design of microwave diodes: high cutoff frequency and low parasitics. Only one epitaxial layer is needed. The Schottky contact is deposited on the slope of a mesa in order to obtain both low series resistance and low capacitance, Up to now, a Zero-bias cutoff frequency of 150 GHz has been achieved. The advantage of this type of diodes as compared to planar diodes produced by double selective epitaxy is the use of standard technology, resulting in good reproducibility and yield.

K. Heime

Papers

A new concept for microstrip-integrated GaAs Schottky-diodes