Band-to-band and sub-band gap cathodoluminescence from GaAsP/GaInP epistructures grown on GaAs substrates

Lattice-matched GaAsxP1−x/GaInP double heterostructures (DHs) are grown on GaAs substrates by step grading the intervening lattice mismatch when image. Cathodoluminescence (CL) measurements on these structures reveal a broad peak approximately 0.15 eV below the band-to-band (BB) emission. While the intensity of the BB peak is strong at room temperature, the sub-band-gap (SBG) feature quenches rapidly between 77 and 300 K. Beam energy-dependent and cross-sectional CL demonstrate that the SBG emission originates in the active layer near the lower interface of the DH. At 77 K, spectrally resolved plan-view CL images show little spatial correlation between the BB and SBG peaks, but when the SBG peak is observed at room temperature, the BB and SBG emission are highly correlated. The temperature-dependent spatial correlation is attributed to differences in thermal quenching of the radiative SBG recombination mechanism.