DISLOCATION-INDUCED DEEP-LEVEL STATES IN IN0.08GA0.92AS GAAS HETEROSTRUCTURES/

We have performed luminescence experiments on In0.08Ga0.92As/GaAs hete rointerfaces to explore the energy distribution of deep level states i n the bandgap for two cases: (1) unrelaxed, pseudomorphic In0.08Ga0.92 As films (200angstrom thick), which have few if any dislocations at th e interface, and (2) partially relaxed In0.08Ga0.92As films (1000angst rom thick) which are expected to have a substantial interfacial disloc ation density. A combined photoluminescence and cathodoluminescence te chnique is used which allows us to profile the sample luminescence thr ough the buried interface region. Our results show the existence of de ep level luminescent features characteristic of the GaAs substrate and features common to In0.08Ga0.99As and GaAs, as well as the existence of a deep level feature near 1 eV photon energy which undergoes a shif t in energy depending upon the degree of strain relaxation in the In0. 08Ga0.92As film. In addition, a deep level feature near 0.83 eV become s prominent only in In0.08Ga0.92As films which have relaxed, and thus contain misfit dislocations at the interface. These deep level differe nces may be due to bandgap states associated with the intrinsic disloc ation structure, impurities segregated at the dislocation, or bulk poi nt defects, or threading dislocations generated during the strain rela xation. Previous work has determined that a deep level state 0.7 eV ab ove the valence band edge would account for the electrical behavior of relaxed In0.08Ga0.92As/GaAs interfaces, which is in good agreement wi th the range of deep level transitions near 0.8 eV photon energy which we observe. These measurements suggest that photo- and cathodolumines cence measurements of deep level emission in these III-V semiconductor s can provide a useful indicator of electrically active defect densiti es associated with misfit dislocations.