Photoluminescence of extended defects in heterostructures with InAlAs metamorphic buffer at different excitation wavelengths

Abstract

We report the observation of photoluminescence (PL) of energy levels presumably associated with extended defects in metamorphic buffer InxAl1–xAs with x = 0.05 → 0.65 at photon energy range of 0.8–1.2 eV, while the quantum well PL was observed at 0.6–0.8 eV. The metamorphic HEMT heterostructures with In0.65Al0.35As/In0.70Ga0.30As/In0.65Al0.35As quantum well (QW) and with different defectiveness degree were studied. Interband excitation by lasers with a wavelength of 409, 450, 532 nm, and subband excitation by infrared (IR) laser with 1064 nm wavelength (with photons energy less than the bandgap of metamorphic buffer layer) both result in the appearance of “defect” PL. Compared to the visible excitation, the IR illumination with the same power density increases “defect” PL intensity in samples with high twins density by an order of magnitude, whereas in more perfect samples with stacking faults and threading dislocations it causes an increase in “defect-to-QW” PL intensities ratio. The study of PL intensity as a function of the pump power in the range of power density 10–3600 W/cm2 reveals that the non-radiative recombination plays an important role during the recombination of photoexcited charge carriers from “defect” levels because the “defect” PL intensity dependence on the pump power density is mainly sublinear while for the QW PL the power law with exponent 1.2–1.4 is observed.