Deep-level defects at lattice-mismatched interfaces in GaAs-based heterojunctions

Electrical properties of lattice-mismatch-induced defects in GaAs/GaAsSb and GaAs/InGaAs heterojunctions have been studied by means of an electron-beam-induced current (EBIC) in a scanning electron microscope and deep-level transient spectroscopy (DLTS). DLTS measurements, carried out with p-n junctions formed at the interfaces, revealed one electron trap and two hole traps induced by the lattice mismatch. The electron trap, at about E c -0.68 eV, has been attributed to electron states associated with threading dislocations in the ternary compound. By comparing the concentration of this trap, revealed by DLTS, with EBIC results on the diffusion length, obtained for heterojunctions with different lattice mismatches, it is inferred that the minority-carrier lifetime is controlled by dislocations in the epilayer region close to the interface. Two new hole traps have been ascribed to defects associated with the lattice-mismatched interface of the heterostructures.