We report a rapid thermal annealing (RTA) enhancement of the structural coherence of Si-implanted InxAl1-xAs (x≊0.54) layers on (100)InP. Under these annealing conditions (750°C for 30 s), the enhancement occurs only in implanted samples and is characterized by the appearance of pendellösung fringes in double-crystal x-ray diffraction. Measurements of the parallel (ε∥) and perpendicular (ε⊥) lattice mismatch show a slight relaxation in ε⊥ during RTA without significant generation of dislocations (ε∥=0). The results suggest an electronic mechanism for the increased efficiency of RTA in implanted samples.