Compound Semiconductor Electronics

The following sections are included:

• INTRODUCTION

• CONTENTS

The following sections are included:

• Introduction

• Principle of Operation

• MESFET Technology
  • Recessed gate MESFET
  • Self-aligned MESFETs

• Simulation and Modeling

• Wide Band Gap Semiconductor MESFETs

• Applications

• References

The following sections are included:

• Introduction

• Qualitative Description of MODFET Operation

• Analytical Description of MODFETs

• Fabrication Process
  • Gate formation
    • T-shaped gate
    • Multifinger gate
    • Dual gate
    • Offset recessed gate
    • Double recessed gate
  • Alloyed ohmic contacts
    • Primer
    • AuGe/Ni metallization for alloyed ohmic contact
    • AuGe/Au metallization for alloyed ohmic contact
    • AuGe/Ni/Au metallization for alloyed ohmic contact
    • Au/Ge/Ni/Ag metallization for alloyed ohmic contact
    • Ni/Ge/Au/Ni/Au metallization for alloyed ohmic contact
  • Non-alloyed ohmic contact
    • WSi metallization
  • Regrown ohmic contacts
  • Channel improvement
    • Synopsis
    • Strained layer channel
    • Striped channel
    • Delta (or lamella) doped channel
    • Superlattice-based channel

• Reliability
  • Synopsis
  • Degradation of ohmic contacts
  • Effect of temperature stress
  • Influence of defects and dislocations
  • Effect of transient radiation

• Applications
  • Monolithic microwave integrated circuits (MMICs)
    • Low-noise amplifiers
    • Power performance

• Conclusion

• Acknowledgements

• References

Recent developments in the physics and technology of III-V compound heterojunction bipolar transistors (HBTs) are reviewed. The technologies discussed are AlGaAs/GaAs, GalnP/GaAs, InP/InGaAs, and AlInAs/InGaAs based heterostructures. WIth current gain cut off frequencies over 100 GHz and maximum oscillation frequencies of about 200 GHz, the III-V compound semiconductor based HBTs have advanced to the point of commercialization. These developments also had the fortuitous effect of providing impetus and theoretical base to advance Si based HBT technologies, such as SiGe HBTs, to advance also. Recent SiGe HBTs, taking advantage of advanced Si processing technologies, have also recorded performances in excess of 100 GHz with applications envisioned in high speed analog-digital converters. While there remain some voids in the fundamental understanding of HBTs, the state-of-the-art of the GaAs HBT technology, concerning reproducibility and reliability, is at a point where problems related to production are at the forefront. The next few years are going to prove interesting with each technology recording improved performance.

Advanced military microwave systems are demanding increased integration, reliability, radiation hardness, compact size and lower cost when produced in large volume, whereas the microwave commercial market, including wireless communications, mandates low cost circuits. Monolithic Microwave Integrated Circuit (MMIC) technology provides an economically viable approach to meeting these needs. In this paper the design considerations for several types of MMICs and their performance status are presented. Multifunction integrated circuits that advance the MMIC technology are described, including integrated microwave/digital functions and a highly integrated transceiver at C-band.

GaAs Schottky barrier diodes are used in heterodyne receiver applications to frequencies as high as 4,000 GHz. The primary application that has driven this technology has been radio astronomy. However, other applications are now also very important, particularly studies of the constituents of the Earth's atmosphere. This paper presents a summary of this increasingly important technology. The requirements that the diodes must meet and the benefits of GaAs Schottky devices are discussed. The optimization of the diodes for frequency mixing and multiplication throughout the frequency range of interest is overviewed. The analysis of terahertz frequency electronic transport in the diodes is then briefly considered with an emphasis on numerical modeling techniques. The typical circuit designs and the efficient coupling of energy are considered, and the state-of-the-art systems are reviewed. Finally, ongoing and future research topics are discussed. It is concluded that although this technology is quite well developed, much remains to be done, particularly in the areas of combining accurate circuit and device simulations for optimization and design purposes and the development of lower cost systems.

The following sections are included:

• Introduction and Overview

• General Requirements for High Speed Digital Circuits

• Material and Process Influences on High Speed Device Performance
  • Importance of materials on device and circuit performance: FETs
  • Importance of materials on device and circuit performance: BJTs
  • Importance of process on device and circuit performance

• Circuits for High Performance Digital ICs
  • Very high speed SSI/MSI circuits
  • Low power high speed LSI/VLSI circuit techniques
    • Static ratioed logic
    • Static non-ratioed logic
    • Dynamic low power high speed circuits
    • Low power bipolar logic

• Conclusions

• Acknowledgment

• References

Electronic and optical devices fabricated from wide band gap semiconductors have many properties ideal for high temperature, high frequency, high power, and radiation hard applications. Progress in wide band gap semiconductor materials growth has been impressive and high quality epitaxial layers are becoming available. Useful devices, particularly those fabricated from SiC, are rapidly approaching the commercialization stage. In particular, MESFETs (MEtal Semiconductor Field-Effect Transistors) fabricated from wide band gap semiconductors have the potential to be useful in microwave power amplifier and oscillator applications. In this work the microwave performance of MESFETs fabricated from SiC, GaN and semiconducting diamond is investigated with a theoretical simulator and the results compared to experimental measurements. Excellent agreement between the simulated and measured data is obtained. It is demonstrated that microwave power amplifiers fabricated from these semiconductors offer superior performance, particularly at elevated temperatures compared to similar components fabricated from the commonly employed GaAs MESFETs.

We review the simulation and modeling techniques used for popular compound semiconductor devices such as the Heterostructure Field Effect Transistor (HFET), the Metal Semiconductor Field Effect Transistor (MESFET), and the Heterostructure Bipolar Transistor (HBT). Starting with the basic transport theory and the numerical simulation techniques based on this theory, we proceed to give examples of Monte Carlo simulations and of 2D balance equation simulations for investigating fundamental device properties and for exploring new design concepts. Next, we present analytical HFET and MESFET models suitable for circuit simulations. These models are based on the so-called universal FET modeling concept, and accurately reproduce FET I-V and C-V characteristics. Finally, we review basic simulation and modeling issues for HBTs.