HgCdTe Growth

CdTe is a II-VI material actively under development as a buffer layer on GaAs for subsequent HgCdTe growth and as a solar eell. CuInSea is also under development for solar cells. Both have bandgaps near 1.5 eV (the peak in the transmitted solar spee-trum). have surpassed the 10% efficiency range, and are relatively cost competitive. However, each of these compounds presents long term environmental pollution concerns. 

Fig. 13. Furnace reactor for the growth of HgCdTe films on CdZnTe substrates usiag the Hquid-phase epitaxial process. The melt is tellurium ia a quartz...

Fig. 14. Phase diagrams of HgCdTe used to defiae the Hquid-phase epitaxial growth process where composition is ia mole fractioa, X, and the numbers represent temperatures ia °C (a) Te-rich corner where the dotted Haes A—F correspoad to values of of 0.1, 0.2, 0.3, 0.5, 0.8, and 0.9, respectively, and (b) Hg-rich corner where A—F correspond to values of X of 0.9, 0.8, 0.6, 0.4, 0.2, and 0.1, respectively.

Fig. 15. Excess carrier concentration in HgCdTe in a saturated Hg vapor as a function of temperature where the dashed line represents Hg vacancies. The extrinsic impurity concentration can be adjusted in the growth process from low 10 up to mid-10. Low temperature annealing reduces Hg vacancy...

Finally, photosensitization is used in wide-area photochemical CVD, because generation of sufficient UV photons over a large area to drive the chemistry directly is difficult. Hg vapor is usually used as a sensitizer, or it is naturally present, as in the growth of HgCdTe (43). Hg is readily excited by an external Hg lamp according to the following reaction ... 

A CdTe layer 12 is formed over the structure by the use of a vapor growth method. Thereafter, an HgCdTe layer 14 is formed over the CdTe layer. 

Mercury cadmium teiluride (HgCdTe) is a direct bandgap semiconductor widely used as a material for infrared detectors due to his narrow variable band gap. The achievement of high-performance detectors depends critically on a low surface recombination velocity of the minority carriers. The chemical growth of a passivation oxidized superficial layer in an aqueous Fe(CN)g3- basic solution is studied in this work. The depth profiles of the different elements in the oxidized layer superficial layer and its thickness are studied by X-ray photoelectron spectroscopy. The electrical properties of the interface are evaluated from MIS devices. The conditions of oxidation have been optimized. 

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