45th Freiburg Infrared Colloquium
9 May 2023
On the 16-17 of May, you can meet us at the 45th Freiburg Infrared Colloquium.
We are the partner of the conference. You can meet our Sales Team and join Łukasz Kubiszyn’s (Expert Epitaxy Engineer) presentation about HOT longwave InAs/InAsSb superlattice cascade photodiodes.
Wednesday, May 17, 2023 / 15:10 – 15:30 / Advanced Detector Topics
We demonstrate HOT LWIR interband cascade photodetectors based on InAs/InAsSb SL heterostructures grown by MBE on GaSb-buffered GaAs substrates. The devices have been monolithically immersed to microlenses prepared from the GaAs substrates by micromachining. The stages of the cascade devices are connected by p++/n++ tunnel junctions.
This design overcomes the two major obstacles to achieving high signal-to-noise ratio and time response performance in conventional HOT photodiodes, namely a very poor quantum efficiency (due to a low diffusion length of charge carriers in the absorber) and a very low resistance of the devices. The operation of the devices was optimized mostly for zero-bias
flicker-free operation at ~300 K or 200 K and wavelength λ~10.6 µm. This was done by modification of the absorber design (thickness, doping, SL parameters) and the number of cascade stages. Mesa photodiodes were processed using photolithography-assisted wet or ICP-RIE etching and vacuum deposition of Au contact layers. The performance of cascade devices is close to that of the best HOT devices offered by VIGO. Further improvements in performance, as well as the extension of operation wavelength, are possible and will be explored. Demonstrated photodetectors open new possibilities for a large variety of applications, e.g. for FTIR and laser spectroscopy.