Advanced materials for GaAs Microwave Devices

Abstract

A number of 111-V compound semiconductors have higher electron mobilities and peak electron velocities than silicon. This makes these materials attractive for use in high-frequency applications. However, the use of these materials was delayed for a number of years by the fact that most of these compounds such as GaAs lack a stable native oxide and display a large interface trap density at the junction with other materials. These problems were overcome in the early 1960s by the development of the MESFET (metal semiconductor FET) where the control electrode was formed by a metal Schottky contact directly onto the GaAs surface. Early devices were fabricated in epitaxial conducting layers deposited, by for example vapor phase epitaxy, onto GaAs substrates. As the quality of these substrates improved, the conducting layers were formed by implantation of silicon ions directly into the substrate surface. The requirement for devices working a t even higher frequencies has necessitated the move from implanted MESFETs to more complicated multi-layer heterostructures, for devices such as HEMTs (high electron mobility transistors) and HBTs (heterojunction bipolar transistors), which can only be produced using epitaxial techniques. In this article the technique of ion-implantation and molecular beam epitax y are described together with a description of HEMTs and HBTs.

Investigation of Localized States in GaAsSb Epilayers Grown by Molecular Beam Epitaxy

“…Gallium Arsenide (GaAs)-based III-V group material systems have been extensively investigated over several decades for optoelectronic applications 1 2 3 4 5 . Band gap tailoring of GaAs-based materials is an important task for hetero-epitaxial devices.…”

Decreasing Defect‐State Density of Al2O3/GaxIn1−xAs Device Interfaces with InOx Structures

“…An oxide/Ga x In 1− x As interface is frequently found as part of various device components (e.g., metal–oxide–semiconductor (MOS) high electron mobility transistor, structure, and IR detectors) currently used in electronics and in the design of many a potential future device (e.g., III–V MOS field‐effect transistor, and tunnel field‐effect transistor) . However, oxide/Ga x In 1− x As interfaces are usually considered as nonoptimized, adversely affecting the device performance: namely, they contain a high density of material defects that cause electronic defect states in the band‐gap area (gap states), which further increase the leakage current, nonradiative recombination, and Fermi‐level pinning, for example.…”

Microwave tunability in a GaAs-based multiferroic heterostructure: Co2MnAl/GaAs/PMN-PT

“…10 In particular, GaAs-based platforms, featuring very low dielectric losses in the rf and microwave bands, are especially attractive for the incorporation of multiferroic elements in a new class of multifunctional monolithic microwave integrated circuits ͑MMMICs͒. 11 The present work reports on the ME properties of a layered multiferroic structure consisting of a ferromagnet grown on GaAs substrate and ferroelectric lead magnesium niobatelead titanate ͑PMN-PT͒. Many Heusler alloys, such as Co 2 MnAl and Co 2 MnSi, 12,13 are expected to be ideal halfmetals with the majority of electrons in one spin state.…”