Infrared detector barrier heterostructures with strained layer superlattice (SLS) absorbers with different periods were compared. The first was a reference using a conventional barrier heterostructure with a low temperature energy gap corresponding to a wavelength of 10  μm in a 2- μm-thick undoped absorber using a 10.9 nm period with InAs/InAsSb0.36 compositions grown directly on a GaSb substrate. The second structure, in contrast, used a significantly shorter 4.3 nm period absorber with InAsSb0.3/InAsSb0.55 compositions, similar energy gap, and absorber thickness, which were grown on a 6.2 Å lattice constant GaIn0.3Sb virtual substrate on GaSb. It was found that in the short period SLS, the vertical hole mobility and minority carrier lifetime in the temperature range of 80–150 K were a factor on 2–3 greater than in the reference structure. The improvement of the vertical hole mobility was attributed to the effect of hole delocalization. The latter results in an increase in the optical absorption coefficient and the quantum efficiency.

We describe an nBp structure comprised of waveguide with gratings for electronic steering a 10.6-µm laser and show that a 0.06 change of the refractive index by carrier injection leads to a 3.5° steering angle.

We describe a GaAs detector array for soft-Xray photons with energies above 250 eV designed to operate with power density levels of up to 20 W/mm2 to be used in a novel beam position monitor.

GaAs photodiode arrays have been designed for non-destructive monitoring of X-ray beam position in soft coherent beamline front ends in synchrotron light sources. A shallow p-on-n junction was employed to reduce the device photocurrent density to optimize the operation with beam power densities up to 20 W/mm2, mainly coming from hard X-rays. With this approach, the photocurrent is primarily defined by the excess carriers generated by low-energy X-ray photons absorbed near the detector surface. The p-n junction structures were grown by Molecular Beam Epitaxy and processed into 64-element linear photodiode arrays. The devices were characterized first in the visible range with a high-power Ar-ion laser and then tested in the soft and hard X-ray regions up to 10 keV at two beamlines of the National Synchrotron Light Source-II. The responsivity was measured to be 0.16 A/W at 0.7 keV and 0.05 A/W at 6 keV in agreement with modeling. At higher X-ray energies the measured responsivity was lower than predicted in the framework of the carrier diffusion model; a possible explanation is discussed.

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