Measurements of carrier recombination rates using a time-resolved pump-probe technique are reported for mid-wave infrared InAs/InAs1−xSbx type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16 K band-gap of ≃235 ± 10 meV was achieved for all five unintentionally doped T2SLs. Carrier lifetimes were determined by fitting a rate equation model to the density dependent data. Minority carrier lifetimes as long as 10 μs were measured. On the other hand, the Auger rates for all the InAs/InAsSb T2SLs were significantly larger than those previously measured for InAs/GaSb T2SLs. The minority carrier and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness.

Temperature-dependent measurements of carrier recombination rates using a time-resolved optical pump-probe technique are reported for mid-wave infrared InAs/InAs 1Àx Sb x type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16 K band-gap of $235 6 10 meV was achieved for five unintentionally and four intentionally doped T2SLs. Carrier lifetimes were determined by fitting lifetime models based on Shockley-Read-Hall (SRH), radiative, and Auger recombination processes to the temperature and excess carrier density dependent data. The minority carrier (MC), radiative, and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness for the unintentionally doped T2SLs. The MC lifetime is limited by SRH processes at temperatures below 200 K in the unintentionally doped T2SLs. The extracted SRH defect energy levels were found to be near mid-bandgap. Also, it is observed that the MC lifetime is limited by Auger recombination in the intentionally doped T2SLs with doping levels greater than n $ 10 16 cm À3. V

A high-performance InGaAs/GaAs vertical quantum dot infrared photodetector (QDIP) with combined barrier of quaternary In 0.21 Al 0.21 Ga 0.58 As and GaAs was investigated in this study. A dominant long wavelength ($10.2 lm) response was observed from the device. The device demonstrates large responsivity (2.16 A/W) with narrow spectral-width (Dk/k $0.14) and high detectivity (1.01 Â 10 11 cm Hz 1/2 /W at 0.3 V) at 10.2 lm at 77 K. In addition, the device has also produced a detectivity in the order of 6.4 Â 10 10 cm Hz 1/2 /W at 100 K at a bias of 0.2 V, indicating its suitability for high-temperature operations. V

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A time- and temperature-dependent differential-transmission technique is used to study the bandgap dependence of Auger recombination in Ga-free InAs/InAsSb type-II superlattices (T2SLs). The bandgap energies are varied between 290 meV (4.3 μm) and 135 meV (9.2 μm) by engineering the layer thickness and alloy Sb concentration. A long-wave infrared structure with 135 meV bandgap energy is found to have an Auger coefficient of 9 × 10−26 cm6/s at 77 K. The measured Auger coefficients increase with decreasing bandgap from approximately 3 × 10−27 cm6/s for mid-wave infrared bandgaps to 2 × 10−25 cm6/s for long-wave infrared bandgaps at 77 K. The measured T2SL Auger coefficients are compared to predicted Auger coefficients for HgCdTe.

At high phonon temperature, defect-mediated electron-phonon collisions (supercollisions) in graphene allow for larger energy transfer and faster cooling of hot electrons than the normal, momentum-conserving electron-phonon collisions. Disorder also affects the heat flow between electrons and phonons at very low phonon temperature, where the phonon wavelength exceeds the mean free path. In both cases, the cooling rate is predicted to exhibit a characteristic cubic power law dependence on the electron temperature, markedly different from the T 4 dependence predicted for pristine graphene. The impact of defect-induced cooling on the performance of optoelectronic devices is still largely unexplored. Here we study the cooling mechanism of hotelectron bolometers based on epitaxial graphene quantum dots where the defect density can be controlled with the fabrication process. The devices with high defect density exhibit the cubic power law. Defect-induced cooling yields a slower increase of the thermal conductance with increasing temperature, thereby greatly enhancing the device responsivity compared to devices with lower defect density and operating with normal-collision cooling.

An InAs/GaAs quantum dot infrared photodetector with strong, multicolor, broadband (5-20 lm) photoresponse is reported. Using a combined quaternary In 0.21 Al 0.21 Ga 0.58 As and GaAs capping that relieves strain and maintains strong carrier confinement, we demonstrate a four color infrared response with peaks in the midwave-(5.7 lm), longwave-(9.0 and 14.5 lm), and far-(17 lm) infrared regions. Narrow spectral widths (7% to 9%) are noted at each of these wavelengths including responsivity value $95.3 mA/W at 14.5 lm. Using strain field and multi-band k Á p theory, we map specific bound-to-bound and bound-to-quasibound transitions to the longwave and midwave responses, respectively. V

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