We have studied the rapid degradation of the AlGaAs/GaAs single quantum well laser diodes on Si substrates grown by metalorganic chemical vapor deposition. The dislocations propagate at velocities up to ∼75 &mgr;m/h along ⟨100⟩ and ∼20 &mgr;m/h along ⟨110⟩, which cause an increase in threshold current and a decrease in differential quantum efficiency. The degraded current–voltage characteristic resulted from the defect‐assisted impurity diffusion. The degradation process occurs very rapidly due to the presence of a high density of defects and thermally induced strain. ©1995 American Institute of Physics.