Interband cascade lasers (ICLs) are a promising light source for the mid-infrared (mid-IR) spectral range. However, for certain applications such as spectroscopic techniques for chemical sensing and non-invasive disease diagnostics, a broadband incoherent radiation source such as an LED may be more desirable. Here we investigate both ICLs and interband cascade light emitting devices (ICLEDs). The ICLEDs follow the example of ICLs by cascading multiple active stages in series to improve efficiency and increase output power, but without an optical cavity to provide feedback.
In this work we will present studies of these devices using high hydrostatic pressure techniques to determine the key efficiency limiting processes so that they might be mitigated. The application of hydrostatic pressure causes reversible changes to the band structure, increasing the energy of the conduction band gamma point and moving other key points in the band structure. This makes it a useful technique to probe recombination processes that depend on band gap and offsets, independently of temperature. For a laser dominated by CHCC Auger recombination, as is typical in narrow band gap devices for the mid-IR, one would expect a decrease in threshold current with increasing pressure, as the Auger process decreases with increasing band gap. However, the lasers studied here exhibit an increase in threshold current with pressure, indicating that other processes also play a significant role. We will discuss the relative contributions from Auger recombination and other processes such as defect-related recombination and carrier leakage in these devices, with respect to relevant modelling.
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