Nanostructured Semiconductor Materials for Mid Infrared Lasers and Detectors

2/11/05 10:30 am 2214 SES (Physics Conference Room )

Sanjay Krishna Assistant Professor, Department of Electrical and Computer Engineering  Center for High Technology Materials, University of New Mexico, Albuquerque NM

In the past few years, there has been active research on investigating emitters and detectors for mid-wave infrared (MWIR, 3-5 mm), long-wave infrared (LWIR, 8-12 mm) and very long wave infrared (>14mm) applications. These applications range from optical remote sensing and night vision cameras to chemical spectroscopy and effluent detection. In my research group, we are investigating three different material systems for mid infrared sensors and emitters. They are:

1. InAs/InGaAs self assembled quantum dots in well (DWELL) Detectors
2. InAs/(In,Ga)Sb strain layer superlattices (SLS) Detectors
3. (In,Ga)Sb/AlInSb metamorphic quantum wells for MWIR Lasers and Detectors

In the DWELL heterostructure, InAs quantum dots are placed in a thin InGaAs quantum well that is in turn placed in a GaAs matrix. Three-color DWELL detectors, operating at 78K, with spectral response in the MWIR (lp1 ~ 4mm), LWIR (lp2 ~ 8mm) and VLWIR (lp3 ~ 23mm) regime have been fabricated in our group. The DWELL system also enables the investigation of novel physics as the carriers relax from the 3D continuum to a 2D quantum well and finally to a quasi-0D quantum dot. Time-resolved dynamics of the carriers were measured using femtosecond pump-probe spectroscopy at 3.9, 7.5, and 10 m. Recently, we have also fabricated the first long wave infrared quantum dot focal plane array (320x256 pixels). Images from this FPA along with the details of our research will be discussed in the presentation.

The second material system we are investigating is the type II InAs/InGaSb superlattice for MWIR/LWIR detection. The material is designed, grown and fabricated in our research group and send to a DOD lab for detailed characterization. We have recently fabricated a high performance InAs/GaSb SLS detector with a 5 mm cut-off operating at 250K.  The growth issues (group V exchange and the interface chemistry) and the structural and optical characterization techniques will be discussed.

The third material system that we are investigating is a metamorphic buffer layer grown on GaAs and GaSb substrates. If the substrate lattice-matching condition is relaxed, type-I (In,Ga,Al)Sb based devices can be grown on GaSb or GaAs substrates. The significant bowing along the InGaSb tie line ensures that IR devices can be grown using only one group V element in the heterostructure. Using a novel digital alloying (DA) technique, a graded InAlSb layer was grown that effectively filters the dislocations caused by the lattice mismatch between the substrate and the buffer layer.  We have obtained room temperature photoluminescence at 3 mm from a InGaSb QW grown on a GaAs substrate.

Acknowledgements:
 I wish to acknowledge my collaborators (Dr. Cardimonas group at AFRL, Prof. Unil Pereras group at Georgia State University, Prof. Painters group at Caltech, Dr. Toni Taylors group at Los Alamos National Laboratory and researchers from ARL) and co-workers ( Prof. L.R. Dawson, Prof. A. Stintz, Dr. P. Dowd, Dr. A. Amtout, G. von Winckel, R.S. Attaluri, E. Plis, S. Annamalai, N.W. Bernstein, D. Formann,  S. Raghavan, P. Hill, R. Kalyanam, and F. Newmann)
Work supported by AFRL, SNL, ARL, ARO, NRO, MDA, MASINT, DOE-BES and NSF

Biography of Presenter:
Sanjay Krishna is an Assistant Professor of Electrical and Computer Engineering at the Center for High Technology Materials at University of New Mexico. Sanjay received his Masters in Physics from the Indian Institute of Technology, Madras in 1996. He completed his MS in Electrical Engineering in May 1999 and received his PhD in Applied Physics in May 2001, both from the University of Michigan, Ann Arbor. He is the recipient of the Outstanding Researcher Award from the ECE Department (2004), IEEE Outstanding Young Engineer Award (2003), Ralph E Powe Junior Faculty Award (2002), NAMBE Best student paper award (1999) and Chilukuri Ramsastry Gold Medal from IIT, Madras (1996). He is the Vice-chair of IEEE/LEOS Albuquerque Chapter and a member of IEEE, SPIE and OSA.