In As ∕ Al Sb high-electron-mobility transistors by molecular-beam epitaxy for low-power applications

Abstract

In As ∕ Al Sb high-electron-mobility transistor technology has transitioned from research to development stages in recent years. Development efforts at Northrop Grumman Space Technology, in collaboration with the Naval Research Laboratory and the University of California, Los Angeles, have focused on X-band and W-band low-noise amplifier monolithic millimeter-wave integrated circuits fabricated for applications requiring ultralow-power dissipation. The materials for the circuits discussed in this article were grown at Northrop Grumman Space Technology on 3-in.-diameter semi-insulating GaAs substrates by molecular-beam epitaxy. Atomic-force microscopy of the as-grown surface on each wafer showed that the rms roughness for all of the wafers ranged between 0.5 and 3.5nm, and this range of roughness was fully compatible with the fabrication process. The high electron mobility that InAs can provide was achieved reproducibly in these materials. It was maintained almost always above 25000cm2V−1s−1, and in several cases even exceeded 30000cm2V−1s−1. The associated electron sheet concentration ranged between 1.2×1012 and 1.8×1012cm−2. These combined mobilities and sheet concentrations gave corresponding sheet resistances in the range of 170±40Ω∕sq, with nonuniformity below 6% over these 3-in.-diameter wafers. These materials characteristics enabled successful fabrication of several recently published X-band and W-band low-noise amplifier circuits, and figures of merit for the circuits that were made specifically from these materials are referenced in this article.