Growth and properties of 40 mm diameter Hg 1−xCd xTe using the two- stage Pressurised Bridgman Method

Abstract

The growth of high quality large 40 mm diameter HgCdTe ( x = 0.210 ) crystals using a new two-stage Pressurized-Bridgman (P-B) method with a starting charge of x = 0.06 has been reported recently (J. Crystal Growth 263 (2003) 273). New information on the equipment which used N 2 -pressurized chambers as safety features for the synthesis and crystal growth stages in order to avoid the explosion of the quartz ampoules due to the high mercury pressure is reported. Detailed characterization studies on crystals grown using this technique are discussed. The investigation showed that the large HgCdTe crystals grown at a low synthesis temperature of 720 °C and a low growth temperature of 710 °C had good compositional uniformity, crystallinity and electrical properties. Double-crystal rocking curve investigations showed that the best full-width at half-maximum was 14.4 arc sec. Both n type and p type wafers could be obtained after a low temperature heat treatment in a Hg atmosphere for about three weeks. Typical n type HgCdTe wafers had a carrier concentrations n 77<2×10 14 cm −3, mobility μ 77>1.2×10 5 cm 2/Vs and minority carrier life-time τ>2.0 μs (the best was 7.4 μs). For p type HgCdTe wafers, the carrier concentration was p 77<1.2×10 16 cm −3, mobility μ 77>500 cm 2/Vs. High performance HgCdTe IR devices have been prepared with these materials demonstrating the state-of-the-art quality of the large HgCdTe crystals.