Effect of optimal rapid thermal alloying of ohmic contacts to microwave pseudomorphic HEMTs

Abstract

Gallium Arsenide (GaAs) pseudomorphic High Electron Mobility Transistors (pHEMTs) are currently used as active devices in manufacturing Monolithic Microwave Integrated Circuits (MMICs) for microwave and millimetre wave applications like Transmit-Receive (T/R) modules in Radars and communication. Low contact resistances (R_c) of pHEMT devices are necessary to obtain low access resistances to the device channel, for enhancement of transconductance and cut-off frequency. Devices formed by optimal and suboptimal conditions of rapid thermal alloying by infra-red optical radiation are investigated using cross-section transmission electron microscopy (XTEM), backside secondary ion mass spectrometry (backside SIMS) and thermal imaging techniques to understand the role of optimal alloy formation and its role in enhancement of device parameters.

KEYWORDS:

• pHEMT
• contact resistance
• AuGeNi
• rapid thermal alloying
• backside SIMS
• XTEM

Acknowledgements

The authors would like to thank Prof. Anand P. Pathak, University of Hyderabad, Hyderabad, for his long association. The authors are also grateful to Late D.V. Sridhara Rao, DMRL, Hyderabad for his help in XTEM studies and technical discussions. The authors kindly acknowledge the Fab and ATQC at GAETEC for help in fabrication, assembly, and testing.