Optical and electrical non-uniformity around dislocations in silicon doped GaAs

Abstract

Highly spatially resolved mappings of photoluminescence (PL) and capacitance-voltage (C-V) measurements have been used to characterise the optical and electrical non-uniformity around dislocations in Si doped GaAs crystals. A broad emission band with a peak at 0.95 eV commonly appears in Si doped GaAs wafers with carrier concentrations ranging from 3 × 1017 to 4 × 1018 cm-3. The average intensity of the 0.95 eV band is lower in the dislocated area than in the dislocation free area. The microscopic intensity pattern of the band agrees with the dislocation pattern. The intensity increases in the core region of dislocations and decreases in the surrounding area. The band edge emission shows a complementary intensity pattern. The C-V mapping of a wafer indicates that the carrier concentration is higher in the dislocated area, correlating with the PL intensity pattern. These results suggest that the microdefects responsible for the 0.95 eV band act as acceptors compensating Si donors and that they are gettered by dislocations.