Annex E. International Armaments Strategy
Army Science and Technology Master Plan (ASTMP 1997)

1. Hetero-Epitaxial Growth For Multidomain Sensors (France)

Description: For future multidomain smart sensors, large area staring HgCdTe Infrared Focal Planes (IRFPAs) will be required. In the current method of producing IRFPAs, the detector array of HgCdTe grown on a CdZnTe substrate and the Si readout array are manufactured separately and then joined by Indium bumps at each pixel. This method cannot be extended to large arrays due to the difference in the thermal expansion coefficient between HgCdTe/CdZnTe and Si.

For the required large area arrays the detector layer has to be grown directly on Si. Due to the large difference in crystal constants between the Si and HgCdTe, this will generally result in low quality HgCdTe layers.

ARL and scientists from LETI (Grenoble, France) are cooperating to develop techniques to grow buffer layers on the Si ending up with high quality CdZnTe. If this is achieved, the growth of the HgCdTe layer can be performed in the standard way.

Dr. Million from LETI visited ARL/NVESD from June through August 1994 working with Nibir Dhar from ARL; a new very promising technique was developed for the growth of these buffer layers. Defect densities were reduced by 2 orders of magnitude--as of today. Work is continuing at ARL and LETI. Nibir will visit LETI next year for a period of about 3 months.

Justification: Besides supporting ASTMP objectives (Chapter IV), the benefits from this cooperative effort are roughly equal for both countries, and each benefited more with the cooperation than had they gone it alone.



Dr. Rodney Smith
Army Materiel Command
5001 Eisenhower Blvd
Alexandria, VA 22333-0001


Mr. Stephen Cohn
Army Research Laboratory
2800 Powder Mill Road
Adelphi, MD 20783-1197