Supercooling studies and LPE growth of Hg1?xCdxTe from Te-Rich solutions |
| |
Authors: | C F Wan D F Weirauch R Korenstein E G Bylander C A Castro |
| |
Affiliation: | (1) Texas Instruments, Incorporated, 75265 Dallas, Texas;(2) Present address: Raytheon Company, Waltham, MA |
| |
Abstract: | Hg1-xCdxTe liquid phase epitaxial (LPE) layers were grown from well-stirred large (100 g) Te-rich Hg-Cd-Te solutions by the dipping
method. Supercooling below the liquidus temperature in Te-rich solutions was studied by differential thermal analysis (DTA)
and film growth results. Although supercooling of 20 to more than 100° C was routinely measured in small (2 g) sample melts,
supercooling in larger melts (>100 g) was erratic and smaller. Factors affecting the degree of supercooling were identified
and a Hg-reflux was found to be a major cause of erratic melt behavior. The LPE reactor was modified to correct the Hg-reflux
action and a visual technique was developed for in situ determination of the liquidus temperature. A limited amount of supercooling
was found in the melt after reactor modification but it was difficult to maintain for extended durations before spontaneous
nucleation occurred. Consequently, programmed cooling rather than isothermal LPE was employed to grow many of the films reported
here. Hg1−xCdxTe epitaxial layers ofx = 0.2 to 0.25 were grown on (111)B oriented CdTe substrates by cooling the melts only 1–2° C below the previously measured
crystallization temperature. The small amount of cooling minimized composition variation with film thickness. Excellent surface
morphology was obtained when slow cooling rates of 0.02–0.05° C/ min were used. Cooling rates greater than 0.2° C/min created
rough, pitted surface. Precise substrate orientation was important in reducing surface terracing. Composition and thickness
uniformities of the epitaxial films were excellent as a result of substrate rotation. Run-to-run reproducibility of film composition
was ±0.01 inx. Hall measurements showed carrier concentrations in the range 2–20 × 1014 cm−3 with photoconductive lifetimes of 0.5–3.0 dms forx = 0.20 to 0.25. |
| |
Keywords: | Liquid Phase Epitaxy Mercury Cadmium Telluride Supercooling |
本文献已被 SpringerLink 等数据库收录! |