Te-RICH DIPPING TECHNIQUE OF HgCdTe LIQUID PHASE EPITAXY

Te-rich dipping technique of HgCdTe liquid phase epitaxy (LPE) was studied. An experimental method was proposed to check the homogenization of (Hg1-xCdx)(1-y)Te-y melt just before the dipping. The gas convection and Hg circumfluence in the growth chamber were suppressed by reducing the free space of gowth chamber. The process control of the growth temperature was improved to suit for the poor temperature reproducibility induced by the gas convection and Hg circumfluence. In this way, the composition reproducibility of MW HgCdTe grown by LPE reaches +/- 0.005. The thickness uncertainty is controlled to be within +/- 5 mu m and the transverse composition uniformity (standard square deviation/average) for 40 x 30mm(2) wafer is less than 1.3 x 10(-3). The differences of the composition and thickness are less than 0.001 and 1 mu m, respectively, for the different wafers grown at the same time. The surface fluctuation of the sample is less than I pm for over 10 mm dimension. It was also observed that, after thermal treatment, our p-type MW HgCdTe epilayers with Hg-vacancy doping have higher hole mobility at 77K compared with the materials grown by other techniques. Besides, compared with horizontal slide LPE, the dipping technique has obvious advantage in the manufacture of large size HgCdTe films and multi-wafers with the same property. Hence, the technique is helpful to develope the batch manufacturing technology of the second generation HgCdTe infrared focal plane array, and it is also significant to develope the splicing of super-large-scale infrared focal plane arrays.