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 deposition, with isopropyl-iodine (IPI) as the dopant source. The memory effect in iodine doping is much smaller than that in indium doping. We confirmed by secondary ion mass spectroscopy (SIMS) measurement that sharp dopant transitions (0.2 mum/decade) were obtained by switching off the IPI during growth. The electron concentration at 77 K was linearly proportional to the dopant partial pressure from 5 X 10(15) to 2 X 10(18) cm-3. We confirmed by SIMS that 20%-100% of the iodine was active as a donor. The Hall coefficient shows classical n-type extrinsic behavior 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.