SB AlertDue to the anticipated winter storm, all classes and in-person events for Monday, Jan. 26 are canceled across Stony Brook Main Campus, Southampton, and Manhattan. Go to Office of Emergency Management for more information.   More information
Skip Navigation
Search
College of Engineering and Applied Sciences
Electrical and Computer Engineering

Paving the Way to Infrared Beam Steering with CMOS Circuits

Paper title: Electrical modulation of the LWIR absorption and refractive index in InAsSb-based strained layer superlattice heterostructures

Authors

  • Jinghe Liu (student), Dmitry Donetsky, Haying Jiang (student), Gela Kipshidze, Leon Shterengas, Gregory Belenky, Dept. of ECE, Stony Brook University, Stony Brook, NY 11794
  • Wendy L. Sarney and Stefan P. Svensson, CCDC US Army Research Laboratory, 2800 Powder Mill Rd, Adelphi, MD 20783.

Venue

J. Appl. Phys. 128, 083101 (2020); Editor’s Pick https://doi.org/10.1063/5.0016149

Novel Technical Contribution

The modulation of refractive index by up to 0.05 with electrical carrier injection was demonstrated in InAsSb-based semiconductor compounds with engineered energy gaps. This change is three orders of magnitude greater than what is achievable in conventional electro-optical materials employed in long-wave infrared wavelength range.

Societal Contribution

Commercially-available electro-optical modulators for free-space longwave infrared laser sources have the bandwidth limited by capacitive cell impedance and require high voltage drivers. The proposed approach enables the device operation with a nanosecond-scale time response with CMOS-compatible voltage and current levels. Low power requirements make it possible to develop arrays of integrated devices for optical beam steering and shaping.

Abstract

InAsSb-based strained layer superlattices (SLS) have strong fundamental absorption, which can be easily modified in a controlled manner by injecting excess carriers. This makes them attractive for intensity modulation of infrared lasers as well as beam steering and spatial beam shaping with a nanosecond-scale time response. This paper reports the modulation of the fundamental absorption and the refractive index by carrier injection in a 3.45-nm-period InAsSb0.65/InAsSb0.35 SLS with a low temperature energy gap of 85 meV grown by molecular beam epitaxy on a GaSb substrate with a GaInSb metamorphic buffer. The SLS absorber was sandwiched by n and p-type wider energy gap layers for electrical injection and confinement of excess carriers. The population of conduction band states was obtained by measuring the intensity modulation of a 10.6 µm CO2 laser for temperatures ranging from T = 77 to 200 K. An increase of the electron quasi-Fermi level with electrical injection up to 20 meV was observed. The experimental data imply a decrease in the Auger coefficient with temperature, from 3 × 1024 cm6/s at 77 K to 1 × 1024 cm6/s at T = 200 K attributed to recombination involving two electrons and a heavy hole. The refractive index changes obtained by electrical injection of excess carriers can reach 0.05 at T = 77 K and 0.035 at T = 200 K, which are at least three orders of magnitude greater than those obtained with electro-optical materials.