We investigated the effects of rapid thermal annealing (RTA)-induced cracks on the diode performance fabricated with GaAs-AlGaAs microstructures. These effects were examined and characterized after quantum-well intermixing within an epitaxial structure capped by either SiO2 or SrF2 layers. The results show clearly that the density of surface crackes strongly depends on the atomic interdiffusion between the well and the barrier layers and on the quality of the dielectric caps as well. Moreover, surface-crack correlation with the RTA process an dielectric deposition parameters, and the cracking effects on diode performance were observed and analyzed in detail. The results demonstrate that diode characteristics can be greatly improved by good surface morphology. Most importantly, we explored an effective way of reducing the density of RTA-induced cracks for the dielectrics grown by plasma-enhanced chemical vapor deposition, which was beneficial for dielectric-cap quantum-well disordering.