Abstract
InAs/InAsSb type-II strained-layer superlattice (SLS) and multiple quantum well (MQW) structures have been studied for their suitability in the active region of mid-infrared LEDs operating at room temperature. A series of InAs/InAs1−xSbx superlattices with low antimony content (x = 3.8–13.5%) were grown by MBE on InAs substrates and characterised using x-ray diffraction and photoluminescence (PL). The 4 K PL spectra of these samples exhibit the expected peak shift to longer wavelength and a reduction in intensity as the Sb content is increased. Band structure simulations highlight the effects of changing the antimony content and the layer thicknesses, to tailor the overlap of the electron and hole wavefunctions and maximise the radiative recombination rate. Analysis of the temperature dependence of the PL emission spectra enabled the extraction of quenching energies that demonstrate some suppression of Auger recombination in both the MQW and SLS structures. The MQW samples exhibit a changeover in the dominant radiative recombination process above ~100 K associated with thermal emission of holes into the InAs barriers; this behaviour was not observed in the SLS samples. These SLS structures have the potential for use as the active region in room temperature mid-infrared LEDs.
Highlights
Detecting and monitoring the presence of gases such as methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2), which have unique absorption spectra within the midinfrared (MIR) spectral range, is desirable for numerous applications in different industries for environmental monitoring because of their harmful effects on the earth’s atmosphere [1]
InAs/InAsSb type-II strained-layer superlattice (SLS) and multiple quantum well (MQW) structures have been studied for their suitability in the active region of mid-infrared Light emitting diodes (LEDs) operating at room temperature
The 4 K PL spectra of these samples exhibit the expected peak shift to longer wavelength and a reduction in intensity as the Sb content is increased
Summary
Detecting and monitoring the presence of gases such as methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2), which have unique absorption spectra within the midinfrared (MIR) spectral range, is desirable for numerous applications in different industries for environmental monitoring because of their harmful effects on the earth’s atmosphere [1]. The eficiency of MIR LEDs at room temperature is signiicantly lower than those operating at visible and near-infrared wavelengths because of detrimental non-radiative Auger and SRH recombination processes In this respect, type-II InAs/InAsSb superlattice structures continue to attract research interest because of the ability to tailor the band structure to target speciic emission wavelengths as well as the potential to adjust electron–hole separation to reduce non-radiative Auger recombination and maximise the rate of radiative recombination [3, 4]. The majority of research to date has focused on the study of InAs/InAsSb structures grown lattice-matched and unstrained onto GaSb substrates [5, 6] comprising
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