Photoreflectance and photoluminescence study of defect passivation by hydrogen in GaAlAs/GaAs/GaAs heterostructures

Using both photoreflectance (PR) at 80 and 300 K and photoluminescence (PL) at 77 K, we have investigated the passivation by H-gun treatment of the surface, interface and volume defects in Ga83Al017As/GaAs/GaAs MBE-grown heterostructure on LEC substrate. Both amplitude of PR and phase delay angle between laser excitation and response were measured. After H-treatment, substantial changes were observed in all properties. Room temperature PR is indicative of the ready disappearance of surface and interface defects at early stages of hydrogenation. Deep trap passivation in the bulk gives rise to increased PL emission in both GaA1As and GaAs, the effect being large only for the latter. A concomitant low in the phase delay angle is detected. The optimum occurs when the total dose of H ions reaching the surface is 1017 cm2. When the largest doses of H are attained, a high density of new bulk defects develops in GaAs, which virtually wipe-out luminescence and reinstate a large phase delay.