Differences in The Growth Mechanism of InxGa1−xAs on GaAs Studied by The Electrical Properties of Al0.3Ga0.7As/InxGa1−xAs Heterostructures (0.2 ≤ × ≤ 0.4)

ABSTRACTLattice mismatched InxGa1−xAs layers with InAs mole fractions below 0.25 grow in a two dimensional growth mode on GaAs. If the thickness of these layers is beyond the critical layer thickness the strain relaxes through misfit dislocations. The misfit dislocation density in the <011> and <01-1> direction differs for n-type layers. This results in a highly anisotropic electron mobility for GaAs/InxGa1−xAs/Al0.3Ga0.7As inverted HEMT structures. A higher electron mobility in the < 011 > direction is measured in comparison to the <01-1> direction. The resistance ratio in the two perpendicular directions exceeds 105. For a three dimensional growth mode, the InxGa1−xAs layer shows interface roughness which degrades the transport properties of the normal Al0.3Ga0.7As/ InxGa1−xAs/ GaAs HEMT structures more than the inverted GaAs/InxGa1−xAs/ Al0.3Ga0.7As HEMT structures. For a three dimensional growth mode, an anisotropic electron mobility for Al0.3Ga0.7As/InxGal, As/GaAs HEMT structures is also observed. For these structures the highest electron mobility is measured in the < 01-1 > direction. This anisotropy could be explained by anisotropic growth rates in the <011> and < 01-1 > directions which results in growth islands with asymmetric extensions.