Mid wave infrared (MWIR) focal plane arrays (FPAs) are very attractive for high contrast thermal imaging in variety of civil, military as well as environmental pollution monitoring applications. Recently, detectors based on InAs/GaSb Type-II superlattice (T2SL) has rapidly advanced for realization of MWIR and LWIR FPAs. T2SL offer numerous advantages including normal incidence absorption, reduced tunneling currents, and suppressed Auger recombination thus resulting in high quantum efficiency and allowing high temperature operation. In this talk, I will present fabrication steps and characterizations of a row-column addressable 128×128 T2SL photodiode array of 8μm square pixels with 2μm separation which is to be addressed by winner-takes-all read-out circuit for speed tracking applications. Low temperature dark currents in the 8μm×8μm array pixel is found to be 780 nA at a reverse bias, V=0.3 V. The peak spectral response of the 8μm×8μm pixel at λ~3.8 μm is measured to be ~0.03 A/W which is, as expected, found to be more than two orders of magnitude better than that of the 200 μm pixel array. Temporal response of these array pixels have been measured to be < 10ns. Next, I will present a Quantum Well Intermixing (QWI) technique, with theoretical study, for isolation of the T2SL pixels without the requirement of conventional mesa etching thus avoid formation of any surface leakage channels. The idea of this technique is to isolate the pixels by forming a more resistive higher band gap material from that of the SL, in the inter-pixel regions.
Sona Das received the M.Sc. degree in Physics with specialization in Electronics from Gauhati University, Guwahati, India in 2006 and M.Tech. degree in Electronics Design and Technology with specialization in optoelectronics from Tezpur Central University, Tezpur, India in 2009. His M.Tech thesis work was accomplished at Central Electronics Engineering Research Institute (CEERI), Pilani, India where he worked on silicon photonic devices for optical communication. He received the Ph.D. degree in Electrical Engineering from the Indian Institute of Technology Kanpur (IIT Kanpur), Kanpur, India in 2018. Presently, He is working as an Assistant Professor in the Department of Electronics and Communication Engineering at K.L University (Deemed to be University), A.P, India. His current research interests include areas of semiconductor optoelectronic materials and devices for next generation Infrared focal plane arrays.