| ABSTRACT |
Amongst all III-V compound semiconductors, the InGaAs-InAlAs materials system has optimum
band structure and transport properties making it the material of choice in many optoelectronics, magnetic and electronic applications. The InGaAs-InAlAs pseudomorphic High Electron Mobility Transistor (pHEMT) devices have also carved an important role in low noise applications using the advantages from engineered epitaxial layer growth and mol fraction modification. However, the conventional low-noise InP pHEMTs currently used in both low-noise amplifier (LNA) and power amplifier (PA) designs suffer from inherently low gate breakdown voltages (VBR) almost regardless of gate length. The typical InP pHEMT¿s VBR is about 6 V or lower, which compromises and complicates LNA designs for rugged, room-temperature radio astronomy (RA)
applications. Thus, this work has been carried out to improve the device breakdown voltages, and, at the same time, uphold the excellent DC and RF performances of the devices. To this effect, two different approaches have been applied; (i) an engineered high-breakdown epitaxial layer structure and (ii) a field modulating structure, leading to robust high breakdown devices that could be of interest for high-efficiency millimetre-wave PAs, as well as robust LNAs that can work with minimal protection circuits. By combining these methods, the resulting devices have led to a novel high frequency and high breakdown InGaAs/InAlAs pHEMT device for high power ¿ low noise application.
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