IODINE DOPING IN MERCURY CADMIUM TELLURIDE (HG1-XCDXTE) GROWN BY DIRECT ALLOY GROWTH USING METALORGANIC CHEMICAL-VAPOR-DEPOSITION

We investigated iodine doping in mercury cadmium telluride (Hg1-xCdxTe ) grown by direct alloy growth using metalorganic chemical vapor depos ition, with isopropyl-iodine (IPI) as the dopant source. The memory ef fect in iodine doping is much smaller than that in indium doping. We c onfirmed by secondary ion mass spectroscopy (SIMS) measurement that sh arp dopant transitions (0.2 mum/decade) were obtained by switching off the IPI during growth. The electron concentration at 77 K was linearl y proportional to the dopant partial pressure from 5 X 10(15) to 2 X 1 0(18) cm-3. We confirmed by SIMS that 20%-100% of the iodine was activ e as a donor. The Hall coefficient shows classical n-type extrinsic be havior from 20 to 300 K. The electron mobility was as high as that in an indium-doped sample. The layer with a Cd fraction of x=0.23, doped to 5 X 10(16) cm-3, exhibited a mobility of 4.7 X 10(4) cm2/V s at 77 K and 6.9 X 10(4) cm2/V s at 20 K. The iodine in the HgCdTe layers was thermally stable. We found no variation in the electrical properties and the iodine depth profile after annealing at 400-degrees-C for 2 h.