Abbes Tahraoui

Very long wavelength infrared type-II detectors operating at 80 K

We report a demonstration of very long wavelength infrared detectors based on InAs/GaSb superlattices operating at T=80 K. Detector structures with excellent material quality were grown on an optimized GaSb buffer layer on GaAs semi-insulating substrates. Photoconductive devices with 50% cutoff wavelength of λc=17 μm showed a peak responsivity of about 100 mA/W at T=80 K. Devices with 50% cutoff wavelengths up to λc=22 μm were demonstrated at this temperature. Good uniformity was obtained over large areas even for the devices with very long cutoff wavelengths.

High-performance quantum cascade lasers (λ∼11 μm) operating at high temperature (T ⩾425 K)

We report record-low threshold current density and high output power for λ∼11 μm Al0.48In0.52As/Ga0.47In0.53As quantum cascade lasers operating up to 425 K. The threshold current density is 1.1, 3.83, and 7.08 kA/cm2 at 80, 300, and 425 K, respectively, for 5 μs pulses at a 200 Hz repetition rate. The cavity length is 3 mm with a stripe width of 20 μm. The maximum peak output power per facet is 1 W at 80 K, 0.5 W at 300 K, and more than 75 mW at 425 K. The characteristic temperature of these lasers is 174 K between 80 and 300 K and 218 K in the range of 300–425 K.

Low-threshold and high power λ∼9.0 μm quantum cascade lasers operating at room temperature

We report a low threshold current density and high power for λ∼9 μmAlInAs/GaInAs quantum cascade lasers operating at room temperature. The threshold current density is 1.95 kA/cm2 at 300 K and 0.61 kA/cm2 at 80 K for 5 μs pulses at 200 Hz repetition rate. The peak output power is 700 mW at room temperature and 1.3 W at 80 K per two facets for cavity length is 3 mm with a stripe width of 20 μm. The characteristic temperature T0 is 185 °C. The slope efficiency is 450 and 800 mW/A at 300 and 80 K, respectively. In continuous wave operation, the output power is more than 150 mW at 80 K and 25 mW at 140 K. This high performance was achieved by improving the material growth and processing technology.

Growth and characterization of type-II nonequilibrium photovoltaic detectors for long-wavelength infrared range

Growth and characterization of type-II detectors for mid-IR wavelength range is presented. The device has a p-i-n structure is designed to operate in the non-equilibrium mode with low tunneling current. The active layer is a short period InAs/GaSb superlattice. Wider bandgap p-type AlSb and n-type InAs layers are used to facilitate the extraction of both electronics and holes from the active layer for the first time. The performance of these devices were compared to the performance of devices grown at the same condition, but without the AlSb barrier layers. The processed devices with the AlSb barrier show a peak responsivity of about 1.2A/W with Johnson noise limited detectivity of 1.1 X 1011 cm X Hz1/2/W at 8 micrometers at 80 K at zero bias. The details of the modeling, growth, and characterizations will be presented.

Growth and characterization of very long wavelength type-II infrared detectors

We report on the growth and characterization of type-II IR detectors with a InAs/GaSb superlattice active layer in the 15-19 micrometers wavelength range. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. The material was processed into photoconductive detectors using standard photolithography, dry etching, and metalization. The 50 percent cut-off wavelength of the detectors is about 15.5 micrometers with a responsivity of 90mA/W at 80K. The 90 percent-10 percent cut-off energy width of the responsivity is only 17meV which is an indication of the uniformity of the superlattices. These are the best reported values for type-II superlattices grown on GaAs substrates.

Growth and optimization of GaInAsP/InP material system for quantum well infrared photodetector applications

Multi-quantum well structures of GaxIn1-xAsyP1-y were grown by metalorganic chemical vapor deposition for the fabrication of quantum well IR photodetectors. The thickness and composition of the wells was determined by high-resolution x-ray diffraction and photoluminescence experiments. The intersubband absorption spectrum of the Ga0.47In0.53As/InP, Ga0.38In0.62As0.80P0.20 (1.55 micrometers )/InP, and Ga0.27In0.73As0.57P0.43 (1.3 micrometers )/InP quantum wells are found to have cutoff wavelengths of 9.3 micrometers , 10.7 micrometers , and 14.2 micrometers respectively. These wavelengths are consistent with a conduction band offset to bandgap ratio of approximately 0.32. Facet coupled illumination responsivity and detectivity are reported for each composition.

High-performance quantum cascade lasers grown by gas-source molecular beam epitaxy

Recent improvements in quantum cascade laser technology have led to a number of very impressive results. This paper is a brief summary of the technological development and state-of- the-art performance of quantum cascade lasers produced at the Center for Quantum Devices. Laser design will be discussed, as well as experimental details of device fabrication. Room temperature QCL operation has been reported for lasers emitting between 5 - 11 micrometers , with 9 - 11 micrometers lasers operating up to 425 K. We also demonstrate record room temperature peak output powers at 9 and 11 micrometers (2.5 W and 1 W respectively) as well as record low 80 K threshold current densities (250 A/cm2) for some laser designs. Finally, some of the current limitations to laser efficiency are mentioned, as well as a means to combat them.

High power 3-12 μm infrared lasers: Recent improvements and future trends

Abstract In this paper, we discuss the progress of quantum cascade lasers (QCLs) grown by gas-source molecular beam epitaxy. Room temperature QCL operation has been reported for lasers emitting between 5– 11 μm , with 9– 11 μm lasers operating up to 425 K . Laser technology for the 3– 5 μm range takes advantage of a strain-balanced active layer design. We also demonstrate record room temperature peak output powers at 9 and 11 μm (2.5 and 1 W , respectively) as well as record low 80 K threshold current densities (250 A / cm 2 ) for some laser designs. Preliminary distributed feedback (DFB) results are also presented and exhibit single mode operation for 9 μm lasers at room temperature.