P A P E R    T I T L E
Comparison of Metamorphic InGaAs/InAlAs HEMT's on GaAs with InP based LM HEMT's

A U T H O R  /  C R E D I T S
K. van der Zanden, M. Behet* and G. Borghs
IMEC, MCP/NMC, Kapeldreef 75, B-3001 Leuven, BELGIUM
Phone: +32-16-281378, Fax: +32-16-281214, e-mail: vdzanden@imec.be

InP based HEMT's have already shown to be the best performing three-terminal devices [1], with excellent performance in the microwave and millimeter wave range. The combination of high gain and low noise has been demonstrated by many realized devices and circuits with operating frequencies up to 100 GHz and beyond [2,3].

A drawback of the InP based system is the substrate itself. Because it is a fairly young technology with limited maturity, the crystal quality is less than for GaAs, resulting in increased brittleness and limited size availability. Up to now, only 2" and 3" substrates are available at relatively high cost per square inch, whereas for GaAs already 6" substrates are available. Additionally, wafer thinning and backside processing have become mature technologies for GaAs.

To combine the advantages of the GaAs substrate with the advantages of InP based heterostructures, metamorphic (MM) InGaAs/InAlAs quantum well structures can be grown on GaAs. The lattice constant of GaAs can be transferred into the one of InP with an appropriate buffer (typically 1 to 2 mm thick), on which the layer stack can be grown lattice matched. The quality of the final heterostructure and thus the device performance, depends fully on the buffer type and quality.

In this paper we will present the results of devices, based on two types of buffer and compare them with the original InP based HEMT's. Both a quaternary buffer (AlGaAsSb) and a ternary buffer (InAlAs) on GaAs will be discussed. All structures have been grown with MBE (Molecular Beam Epitaxy).