The enthalpy of formation of (110) and (001) (GaAs)m(AlAs)n superlattices has been calculated within the local-density scheme. For all cases studied, (m,n) ranging from (1,1) to (7,7), positive enthalpy values are found. Thus, all the superlattices are unstable with respect to disproportionation into the bulk constituents. The enthalpy of formation of (110) and (001) interfaces are calculated to be 23 and 14 meV/interface, respectively. The Ga-3d states do not significantly contribute to the (in)stability of the superlattices.
 

Solid State Communications, 68 959-62, 1988.