P-channel strained single quantum well field effect transistors

One possible solution which has been proposed is the use of material incorporating a biaxial strain, lifting the degeneracy of the valence bands, thus giving light holes. Such material can be obtained in practice by growing epitaxial layers of III-V compounds with slightly different lattice parameters. Provided the layer thicknesses are kept small the resulting strain is not relieved by dislocations and is thus incorporated into the layers. The most popular material system for such strained structures has been In_xGa_1-xAs grown on a GaAs substrate. In this system the In_xGa_1-xAs has the larger natural lattice parameter but it is forced to take up the lattice parameter of the GaAs and is therefore under biaxial compression. This should cause holes travelling in the plane of the In _xGa_1-xAs to exhibit a low effective mass, and such light holes have been observed directly. This paper reports progress in the growth, fabrication and assessment of structures suitable for p-channel FETs