ABSTRACT
Rarely is heteroepitaxial growth lattice matched. In almost all cases of interest, the epitaxial layer has a relaxed lattice constant that is different from that of the substrate. The lattice mismatch strain* (misfit strain) can be defined as
f
a a a
e ≡
−
,
(5.1)
where: as is the relaxed lattice constant of the substrate ae is the relaxed lattice constant of the epitaxial layer
The absolute value of the lattice mismatch may exceed 10%, but is much smaller in many heteroepitaxial systems of practical interest in the field of semiconductors. The mismatch may take on either sign, with some interesting differences observed between tensile ( f > 0) and compressive ( f < 0) systems. This chapter is concerned with several important aspects of mismatched heteroepitaxial growth: (1) the critical layer thickness, (2) the lattice relaxation and introduction of dislocation defects, and (3) the dynamics of dislocation reactions and removal from thick, mismatched layers. Moreover, the main focus of this chapter is on the discussion of equilibrium and kinetically limited relaxation of a single layer with uniform composition on a substrate.
