Type-II InAs/GaSb Superlattices: Physical Understanding and Barrier Engineering

Event Date: 

Monday, May 14, 2012 - 2:00pm

Event Location: 

  • Room 1008 Bldg 937

Event Contact: 

Speaker:

Nutan Gautam - Center for High Technology Materials, University of New Mexico

Type-II InAs/GaSb Strained Layer Superlattice (T2SL) is an emerging technology for infrared detection. They are being seen as a threat to 50 years old incumbent technology based on Mercury-Cadmium-Telluride (MCT) system. T2SL have been theoretically predicted to outperform MCTs. However, it still needs a lot of work in the physical understanding and detector designs of T2SL.
This talk will focus on the molecular beam epitaxy (MBE) growth optimization, physical understating, and heterojunction barrier engineering of T2SL, in midwave infrared (MWIR) and longwave infrared (LWIR) regimes, for performance improvement of photodetectors. We have optimized the interfaces between the individual layers (InAs and GaSb) in T2SL for improving the detector performance. The analysis was carried out using variable temperature photoluminescence response, and use of detector performance parameters such as responsivity, detectivity and dark current. Minibands in strained layer superlattices are not very well understood. We carried out polarization sensitive photocurrent spectroscopy on MWIR and LWIR T2SL material, and correlated experimental results with theoretical simulations to unambiguously establish the ordering of valence minibands in T2SL system.
Heterojucntion barrier engineering of T2SL photodiodes has been carried out in this work, using unipolar current blocking layers to reduce various components dark currents, and hence increasing the temperature of operation. The detector architecture, pBiBn, has demonstrated performance comparable to the state of the art in T2SL technology in LWIR regime. We have also demonstrated multi-color detection using heterojunction barrier engineering. An interband cascade MWIR detector has been demonstrated with
operation upto 420K.