Infrared Photodetectors

Staff: P. Christol, J.P. Perez, J.B. Rodriguez

PhD students: R. Taalat (thèse DGA 2010-2013) ; M. Delmas (MEN, 2012-2015) ; R. Rossignol (MEN, 2014-2017).

Objective :

The objective is the study of cooled photodetectors made of (In,As)Sb structures and InAs/GaSb or InAs/InAsSb type II superlattices (T2SL) in pin and nBn architectures. These Sb-based detectors should be able to improve the signal to noise ratio in order to satisfy the criteria of high performance and SWAP (Size, Weight and Power) requirements with high operating temperature (T > 150K) in the Midwave IR (MWIR 3-5µm). Recently, our activity on T2SL detectors focused the longwave IR (LWIR 8-12µm) and Very Longwave (VLWIR l>12µm) spectral domains in order to address some specific astronomy and defense applications. All details can be found in the corresponding publications.

Recent results :

One of the main property of the T2SL is its flexibility in term of period composition (InAs-rich versus GaSb-rich structure), type of residual doping (p-type versus n-type), choice of superlattice period (InAs/GaSb versus InAs/InAsSb). Since several years, IES collaborates with DOTA's group of ONERA Palaiseau, the french aerospace lab, for a better understanding of such promising detector technology. Combining low dark current and high quantum efficiency, a p-type doped InAs-rich T2SL single pixel pin photodiode, showing performances at the state of the art in the MWIR domain, has been fabricated and characterized (july 2014).

Influence of the p-type doping on the radiometric performances of "InAs-rich" T2SL MWIR photodiode (collaboration I. Ribet-Mohamed, E. Giard PhD Thesis, ONERA).

Among T2SL properties, one of the main interesting is that several structures, with different InAs to GaSb thickness ratios R in each SL period, can target the same cut-off wavelength. Three devices with different SL periods, but the same cut-off wavelength at 5 µm at 77 K, were grown by MBE. The optical and electrical characteristics performed showed the strong influence of the SL composition on both the material properties and photodetector performances, such as the background doping concentration, shape of the response spectra and the dark current measurements. Such result highlights the flexibility property of T2SL photodetectors (January 2014).

Influence of the period thickness and composition on the electro-optical properties of InAs/GaSb T2SL MWIR photodetectors (R. Taalat PhD thesis)

Performed in the framework of the ANR INTREPID project, the first "InAs-rich" T2SL MWIR FPA (TV/4 format) has been realized (December 2013).

From epitaxial growth up to IR imaging : first realization of "InAs-rich" T2SL MWIR FPA (ANR INTREPID project : IES, LPN, CEA-Leti, ONERA)