THE MEASUREMENT OF DEEP LEVEL STATES CAUSED BY MISFIT DISLOCATIONS IN INGAAS/GAAS GROWN ON PATTERNED GAAS SUBSTRATES

Rectangular Schottky diodes were fabricated on In0.06Ga0.94As grown by organometallic vapor phase epitaxy on GaAs substrates patterned with mesas. The density of alpha and beta-misfit dislocations at the strained-layer interface changed with the size of the rectangular mesas. Since all mesas (four sizes and two orientations) are processed simultaneously, all other defect concentrations are expected to remain constant in each diode. Scanning cathodoluminescence showed that the misfit dislocation density varied linearly with rectangle size. Deep-level transient spectroscopy showed that an n-type majority-carrier trap is present at 0.58 eV below the conduction band with a concentration that increases with increasing alpha-type misfit dislocation density. The beta-misfit dislocation density had no influence the deep level spectra, indicating that this trap is related to the cores of only alpha-type misfit dislocations. The capture rate trend corroborates the view that the trap is associated with the dislocation cores and not with isolated defects. Calculations indicate that the trap concentration is comparable to the concentration expected if all of the dislocation core atoms are electrically active.