Photoreflectance and photoluminescence investigations of a step-like GaInNAsSb∕GaAsN∕GaAs quantum well tailored at 1.5μm: The energy level structure and the Stokes shift

Abstract

The energy level structure of a step-like GaInNAsSb/ GaNAs/ GaAs quantum well ͑QW͒ has been investigated by photoreflectance ͑PR͒ spectroscopy and was analyzed by theoretical calculations. In the active region of this structure, i.e., GaInNAsSb/ GaNAs QW, we have observed PR resonances related higher order QW transitions in addition to the ground state transition. Based on calculations from experimental data, we have found that the electron effective mass in the active QW is 0.12m 0 and the conduction band offset for GaInNAsSb/ GaAs interface is about 0.85. The emission observed from this structure at 10 K has a small Stokes shift ͑i.e., 6 meV and Ͻ2 meV for as-grown and annealed structures, respectively͒ and is without the exponential-like tail at the low-energy side. Hence, we conclude that the incorporation of Sb atoms into GaInNAs alloy helps to achieve QW structures which emit light at longer wavelength and have quite narrow emission line and small Stokes shift.

Development of GaInNAsSb alloys: Growth, band structure, optical properties and applications

“…The bandgap line up for this system was investigated by photoreflectance in Ref. [72]. It has been found that this QW has deep enough confinement potential for both electrons and heavy-holes.…”

“…Such an approach has been applied to study the bandgap line-up in our materials, i.e. GaNAsSb/GaAs, GaInNAsSb/GaAs and GaInNAsSb/GaNAs/GaAs step-like QWs [20,[69][70][71][72].…”

Contactless electroreflectance of GaInNAsSb/GaNAs/GaAs quantum wells emitting at 1.5–1.65 μm: Broadening of the fundamental transition

“…In this work we applied contactless electroreflectance ͑CER͒ to study the quality of two generations of GaInNAsSb lasers grown and annealed at various conditions: ͑i͒ the previous generation of GaInNAsSb lasers grown at 20X V-to-III flux ratio at 440°C and annealed at high temperatures ͑760°C͒ for short time ͑10-120 s͒, 3 ͑ii͒ the present generation of GaIn-NAsSb lasers grown at lower V-to-III flux ratio ͑11X͒ at 440°C and annealed at lower temperatures ͑660-720°C͒ for longer time ͑10-60 min͒. 11 So far, electromodulation spectroscopy ͑photoreflectance and CER͒ was mostly used to investigate the band structure for as-grown GaInNAsSb QWs, [12][13][14] including GaInNAsSb/ GaNAs/GaAs laser structures. 12,14 This technique, due to its absorptionlike character, is insensitive to point defects ͑nonradiative centers͒ unlike to PL where the intensity is directly sensitive to nonradiative centers.…”

“…11 So far, electromodulation spectroscopy ͑photoreflectance and CER͒ was mostly used to investigate the band structure for as-grown GaInNAsSb QWs, [12][13][14] including GaInNAsSb/ GaNAs/GaAs laser structures. 12,14 This technique, due to its absorptionlike character, is insensitive to point defects ͑nonradiative centers͒ unlike to PL where the intensity is directly sensitive to nonradiative centers. However, the broadening of CER resonances is very sensitive to energy gap fluctuations, which influence carrier localization and quantum efficiency of PL.…”

“…Relevant details of these calculations are discussed in our previous papers. [12][13][14] CER resonances, which are observed for the as-grown sample from set A, were analyzed in details in Ref. 14.…”