US research activities on InP-based microwave and millimeter-wave devices and circuits

Abstract

Historical PerspectiveFor the past 10-15 years there has been a growing interest in the development of very high performance microwave and millimeter-wave devices and circuits on InP substrates. Indeed, many of the records for noise figure, frequency of operation, power, etc. are held by InP-based devices and circuits. The U.S. has been and continues to be the leader in this field, primarily because the U.S. Department of Defense is a major source of funding for this work and is seen as the major customer for the resulting products. The recent successes of high-technology weapons in the Gulf War can only increase the interest of DoD and the U.S. Congress in advanced technologies such as InP-based microwave/millimeter-wave IC's.In the late 1970's to early 1980's much of the research on InP-based devices centered around IMPATTs and Gunn diodes. These InP devices provided higher peak powers, higher gains, and higher operating frequencies than similar devices based on GaAs or silicon. This made it possible, for example, to develop solid-state transmitters for low power radars. U.S. companies, such as Varian, are marketing InP IMPATTs and Gunn diodes. Allied-Signal, as an example, manufactures a weather radar containing InP IMPATTs for commercial aircraft.In the early to mid-1980's, there was an emphasis on research on InP MISFETs. This work was stimulated by three properties of InP:1. The Fermi level can be unpinned at the InP surface. Electrons in InP have very high peak and saturation velocities.3. InP has a higher thermal conductivity than GaAs.These properties pointed toward excellent microwave and millimeter-wave InP power FETs. They also encouraged work on normally-off, accumulation-mode or inversion-mode devices having low quiescent power. Many of these promises were realized in U.S. research labs. However, the InP MISFET did not progress toward a marketable product primarily because its electrical characteristics were not stable.From the late 1980's to the present, research on InP-based microwave/millimeter-wave devices has centered around FETs and HBTs containing various heterostructures of InP, InGaAs, and InAIAs. The emphasis of this research has been to push fT, f, , , , and noise figure to the limits imposed by the materials involved. The records for these performance measures are held by InP-based devices with improvements being reported continually in the technical literature. Many of these devices are being used in monolithic IC's, which also exhibit record performances in the microwave/millimeter-wave spectrum. xix _ _ -~