An investigation was made of the evolution of the structural and electronic properties of highly mismatched films having thicknesses which ranged from 0.1 to 1.5μm. Atomic force microscopy, cross-sectional transmission electron microscopy and high-resolution X-ray diffraction results showed that the 0.1μm films were almost fully relaxed and consisted of partially coalesced islands which apparently contained threading dislocations at their boundaries. As the film thickness increased above 0.2μm, island coalescence was completed and the residual strain was reduced. Although the epilayers relaxed equally in the <110> in-plane directions, epilayer rotation about an in-plane axis (epilayer tilt) was not equal in both <110> in-plane directions. It was noted that the island-like surface features tended to be preferentially elongated along the axis of epilayer tilt. Epilayer tilt which increased the substrate off-cut (reverse tilt) was evident in the [110] direction. High-resolution transmission electron microscopy indicated that both pure-edge and 60° misfit dislocations contributed to strain relaxation. In addition, as the film thickness increased, the threading dislocation density decreased while the corresponding room-temperature electron mobility increased. Other structural features, including the residual strain and the surface and interface roughnesses, did not appear to affect the electron mobility in these films. The overall results suggested that free-carrier scattering from threading dislocations was the main room-temperature mobility-limiting mechanism in highly mismatched InSb films. It was shown quantitatively that free-carrier scattering from the lattice dilation which was associated with threading dislocations, rather than scattering from a depletion potential surrounding dislocations, was the predominant factor which limited the electron mobility.

Evolution of Structural and Electronic Properties of Highly Mismatched InSb Films. X.Weng, R.S.Goldman, D.L.Partin, J.P.Heremans: Journal of Applied Physics, 2000, 88[11], 6276-86