ABSTRACTWe have discovered a surface instability in In.₂₅GaAs.₇₅/GaAs (100) grown by molecular beam epitaxy (MBE) by direct comparison of atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) investigations. While slipline spacings measured by AFM correspond fairly well with those measured by TEM and SEM, the height displacement measured by AFM was seven times greater than that inferred from dislocations observed with TEM; the number of dislocations are insufficient to produce such dramatic heights. The difference in height measured by AFM with respect to the theoretical height calculated by strain relaxation and TEM dislocation number measurement can be attributed to a surface instability.