ABSTRACT
The metamorphic growth process has enabled the development
of high quality epitaxial films on lattice mismatched substrates
beyond the limitations of pseudomorphic growth. This capability
has permitted the fabrication of new device structures as well as
less expensive existing structures. The metamorphic approach has
been applied to several material systems and device structures
and is illustrated here for the InAlAs/InGaAs/GaAs high electron
mobility transistor (HEMT). The constraints of lattice matching
and pseudomorphic growth are first examined to develop the
motivations for metamorphic growth. Various material properties
of metamorphic films and metamorphic HEMT (MHEMT) structures
on GaAs are characterized. Examples of microwave devices and
circuits incorporating GaAs metamorphic HEMTs are given. A new
application of integrating GaAs metamorphic circuits with silicon
CMOS on a common silicon substrate is presented. Finally, reliability
results of metamorphic HEMTs are reviewed.
