Thermomigration of Te precipitates and improvement of (Cd,Zn)Te substrate characteristics for the fabrication of LWIR (Hg,Cd)Te photodiodes |
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Authors: | H R Vydyanath J A Ellsworth J B Parkinson J J Kennedy B Dean C J Johnson G T Neugebauer J Sepich Pok-Kai Liao |
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Affiliation: | (1) Aerojet Electronic Systems Division, 1100 W. Hollyvale Street, 91702 Azusa, CA;(2) U.S. Army CECOM Night Vision and ElectroOptics Directorate, 22060 Fort Belvoir, VA;(3) II-VI Inc., 375 Saxonburg Boulevard, 16056 Saxonburg, PA;(4) Texas Instruments, Inc., 75265 Dallas, TX |
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Abstract: | (Cd,Zn)Te wafers containing Te precipitates have been annealed under well defined thermodynamic conditions at temperatures
below and above the melting of Te. Results of the examination of the wafers with infrared microscopy before and after the
anneals indicate a substantial reduction of the Te precipitates in wafers annealed at temperatures in excess of the melting
point of Te compared with those annealed at temperatures below the melting point of Te. These results confirm the thermomigration
of liquid Te precipitates to be the principally operative mechanism during annealing in the elimination of these precipitates
in (Cd,Zn)Te wafers. The occurrence of Te precipitates in (Hg,Cd)Te epitaxial layers grown on (Cd,Zn)Te substrates containing
Te precipitates is also explained on the basis of thermomigration of these precipitates during LPE growth from the substrates
to the epilayers. Absence of occurrence of Te precipitates in (Hg,Cd)Te epilayers grown on annealed (Cd,Zn)Te substrates with
negligible Te precipitates is also confirmed. Usefulness of annealing (Cd,Zn)Te substrates—to eliminate Te precipitates—prior
to epilayer growth is confirmed via demonstration of improved long wavelength infrared (Hg,Cd)Te device array performance
uniformity in epitaxial layers grown on (Cd,Zn)Te substrates with negligible Te precipitates after annealing. |
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Keywords: | CdZnTe substrates LPE LWIR HgCdTe device arrays thermomigration of Te LPE |
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