The Study on Fabrication and Characterization of Al0.2In0.8Sb/InAs0.4Sb0.6 Heterostructures by Molecular Beam Epitaxy

Al
_0.2
In
_0.8
Sb/InAs
_0.4
Sb
_0.6
heterostructures have been successfully grown on GaAs substrate by molecular beam epitaxy (MBE). The influence of three different metamorphic buffer layers on the transport properties and crystal quality of the samples has been investigated, which shows the highest electron mobility of 28000 cm
²
/V·s and the two-dimensional electron gas (2DEG) concentration of 9.29×10
¹¹
cm
^-2
at 300 K are obtained in the sample with a Al
_0.2
In
_0.8
Sb metamorphic buffer layer. This result is attributed to a decrease in both dislocations and interface roughness scattering for sample A3 with an Al
_0.2
In
_0.8
Sb metamorphic buffer layer. Meanwhile, a series of samples were grown in order to systematically study the effects of channel layer width, spacer layer width, and Si δ-doping density on the transport properties in the Al
_0.2
In
_0.8
Sb/InAs
_0.4
Sb
_0.6
modulation-doped heterostructures. The scattering mechanisms of interface roughness scattering, dislocations scattering, polar optical phonon scattering, remote impurity scattering, alloy scattering, and inter-subband scattering have been discussed to examine their effect on electron mobility and the 2DEG concentration. The results show that the highest electron mobility of 26500 cm
²
/V·s and the 2DEG concentration of 1.15×10
¹²
cm
^-2
at 300 K can be achieved in the Al
_0.2
In
_0.8
Sb/InAs
_0.4
Sb
_0.6
modulation-doped heterostructures with a 30-nm channel, a 6-nm spacer layer width, and a 9.0×10
^-18
cm
^-3
Si δ-doped layer.