In the mid-infrared (Mid-IR), arrays of distributed feedback Quantum Cascade Lasers (QCL) have been developed as a
serious alternative to obtain extended wavelength operation range of laser-based gas sensing systems. Narrow-linewidth,
single mode operation and wide tunability are then gathered together on a single chip with high compactness and
intrinsic stability. In order to benefit from this extended wavelength range in a single output beam we have developed a
platform for InP-based photonics. After the validation of all required building blocks such as straight waveguides,
adiabatic couplers between active and passive waveguides, and echelle grating multiplexers, we are tackling the
integration into a single monolithic device.
We present the design, fabrication and performances of a tunable source, fully monolithic based on the echelle grating
approach. Advantages are design flexibility, relatively simple processing and the need for one single epitaxial growth for
the entire structure. The evanescent coupler has been designed to transfer all light adiabatically from the active region to
a low loss passive waveguide, while taking advantage of the high gain available in the quantum wells. The multiplexer is
based on an etched diffraction grating, covering the whole range of the 30 lasers of the array while keeping a very
compact size. These results show the first realization of a monolithic widely tunable source in the Mid-IR and would
therefore benefit to the development of fully integrated spectroscopic sensor systems.
In this communication, we report results obtained on a new InSb/InAlSb/InSb ‘bariode’, grown by MBE on (100)-
oriented InSb substrate. Because of a very weak valence band offset with InSb (~ 25meV), InAlSb is a good candidate as
a barrier layer for electrons. However, due to lattice mismatch with the InSb substrate, careful growth study of InAlSb
was made to insure high crystal quality. As a result, InSb-based nBn detector device exhibits dark current density equals
to 1x10<sup>-9</sup>A.cm<sup>-2</sup> at 77K: two decades lower than Insb standard pin photodiode with similar cut-off wavelength.
Moreover, compared to standard pn (or pin) InSb-based photodetectors fabricated by implanted planar process or by
molecular beam epitaxy (MBE), we demonstrate that the reachable working temperature, around 120 K, of the InSbbased
nBn detector is respectively higher than 40 K and 20 K than the previous. Such result demonstrates the potentiality
of Insb detectors with nBn architecture to reach the high operating temperature.
In this communication, the potentiality of InSb material as an avalanche photodiode (APD) device is
investigated. Current density-voltage (J-V) characteristics at 77K of InSb pin photodiodes were simulated by
using ATLAS software from SILVACO, in dark conditions and under illumination. In order to validate
parameter values used for the modeling, theoretical J-V results were compared with experimental
measurements performed on InSb diodes fabricated by molecular beam epitaxy. Next, assuming a
multiplication process only induced by the electrons (e-APD), different designs of separate absorption and
multiplication (SAM) APD structure were theoretically investigated and the first InSb SAM APD structure
with 1μm thick multiplication layer was then fabricated and characterized.
InSb pin photodiodes and nBn photodetectors were fabricated by Molecular Beam epitaxy (MBE) on InSb
(100) n-type substrate and characterized. MBE Growth conditions were carefully studied to obtain high
quality InSb layers, exhibiting in pin photodiode design dark current density values as low as 13nA.cm<sup>-2</sup> at
-50mV and R0A product as high as 6x10<sup>6</sup> WΩcm<sup>2</sup> at 77K. Then, a new unipolar nBn InSb/InAlSb/InSb detector structure on InSb substrate were designed in order to suppress generation-recombination dark
current. The first InSb nBn devices were fabricated and preliminary electrical characterizations are reported.