MBE growth and characterization of MODFET heterostructures using pseudomorphic InGaAs or InAs/GaAs superlattice channels

We studied the influence of the growth temperature T
s
and of the InGaAs quantum-well channel thickness d
ch
on the 300 and 77 K Hall electrical properties of pseudomorphic MODFET-type heterostructures grown by molecular-beam epitaxy (MBE). In agreement with Nguyen et al., we find an optimum channel thickness of 90 A for an indium composition y =0.25 of the channel. Significant improvements in sheet resistivity p
s
and in carrier concentration n
so
were obtained by using AlGaAs doped barriers on both sides of the pseudomorphic channel. We were thus able to obtain a 2DEG sheet density n
so
as high as 4.0x10
¹²
cm-2 at 77 K, which is among the highest values reported for MODFETs on GaAs. Promising results were obtained on MODFET's using an (InAs)
m
(GaAs)
n
short period superlattice for the channel.