Abstract
The in-plane and cross-plane thermal conductivities of the cladding layers and active quantum wells of interband cascade lasers and type-II superlattice infrared detector are measured by the 2-wire 3ω method. The layers investigated include InAs/AlSb superlattice cladding layers, InAs/GaInSb/InAs/AlSb W-active quantum wells, an InAs/GaSb superlattice absorber, an InAs/GaSb/AlSb M-structure, and an AlAsSb digital alloy. The in-plane thermal conductivity of the InAs/AlSb superlattice is 4–5 times higher than the cross-plane value. The isotropic thermal conductivity of the AlAsSb digital alloy matches a theoretical expectation, but it is one order of magnitude lower than the only previously-reported experimental value.
Highlights
III-V antimonide infrared (IR) detectors typically operate cryogenically [1, 2], whereas the latest generation of midwave IR lasers operates at room temperature [3, 4]
The in-plane and cross-plane thermal conductivities of the cladding layers and active quantum wells of interband cascade lasers and type-II superlattice infrared detector are measured by the 2-wire 3ω method
The interband cascade laser (ICL) consists of a thin active core (200-300 nm) sandwiched between somewhat thicker GaSb separate-confinement layers, which are in turn enclosed by top (1-1.5 μm thick) and bottom (3-4 μm thick) InAs/AlSb superlattice (SL) cladding layers
Summary
III-V antimonide infrared (IR) detectors typically operate cryogenically [1, 2], whereas the latest generation of midwave IR (mid-IR) lasers operates at room temperature [3, 4]. Thermal simulations indicate that in this scenario, the most significant thermal bottleneck is the cross-plane thermal conductivity of the InAs/AlSb SL comprising the top cladding This physical quantity has been investigated in one previous publication [6], not for the SL layer thicknesses employed in current state-of-the-art ICL designs. It seems reasonable to assume that the active core of the ICL (InAs/GaInSb/InAs/AlSb repeated layers), the bulk of of which consists of an InAs/AlSb electron injector, is thermally similar to the cladding SL The accuracy of this assumption will require verification in the future, and its effect on the ICL thermal impedance may become greater for ICLs with more stages for higher cw output power. Because the dark currents of mid-IR and LWIR PDs and detectors can increase by several orders of magnitude with temperature [2], it is important to calibrate the thermal conductivities of the active and barrier layers. While the cross-plane thermal conductivities of InAs/AlSb SLs [6], AlAsSb digital alloys [8], and T2SLs [9] have been measured previously, to the best of our knowledge the in-plane thermal conductivities have never been reported
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