HgCdTe

More reeently, HgCdTe array deteetors have beeome available that respond in the range 3500-900 enC ... 

Fig. 4. Sensitivity as a function of detector temperature showing (—) experimental results for HgCdTe (H and A) Hg CdTe, x = 0.185 and x = 0.280,...

Fig. 8. The photodiode detector (a) band model where the photon generates electron—hole pairs that are separated by the built-in potential setting up a photocurrent (b) physical model for a planar diode. The passivation is typically Si02 for Si diodes, an In oxide for InSb diodes, and CdTe for HgCdTe...

In the x-ray portion of the spectmm, scientific CCDs have been utilized as imaging spectrometers for astronomical mapping of the sun (45), galactic diffuse x-ray background (46), and other x-ray sources. Additionally, scientific CCDs designed for x-ray detection are also used in the fields of x-ray diffraction, materials analysis, medicine, and dentistry. CCD focal planes designed for infrared photon detection have also been demonstrated in InSb (47) and HgCdTe (48) but are not available commercially. 

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...

For a weU-designed, weU-made HgCdTe photoconductoi detector (76,77), g-r noise is dominant and may be expressed in terms of a minority carrier densityp and majority carrier density n. Semiconductor noise analysis for the HgCdTe photoconductor yields,... 

HgCdTe photodiode performance for the most part depends on high quantum efficiency and low dark current density (83,84) as expressed by equations 23 and 25. Typical values of at 77 K ate shown as a function of cutoff wavelength in Figure 16 (70). HgCdTe diodes sensitive out to a wavelength of 10.5 p.m have shown ideal diffusion current limitation down to 50 K. Values of have exceeded 1 x 10 . Spectral sensitivities for... 

Fig. 16. Resistance area (R ) product for HgCdTe photodiodes cooled to 77 K. The soHd line represents the theoretical limit, the dashed lines (—) and (- -) high and low performance, respectively. Dark current caused by defects lowers R and detector sensitivity. In the high performance range dark...

An extensive compilation of the properties of compound semiconductors may be found in the Landolt-Bn mstein reference books (13,14). Various subvolumes in the series cover the properties of elemental. III—V, II—V, and other less common semiconductors. Information may also be found concerning semiconductor technology. Another useful source of information is the EMIS data review series (15). These books describe the properties and technology of GaAs, HgCdTe, InP, AlGaAs, InGaAs, and the III—V nitride compounds. 

Electronic and Optoelectronic Applications of TeUurides. Most metal teUurides are semiconductors with a large range of energy gaps and can be used in a variety of electrical and optoelectronic devices. AUoys of the form HgCdTe and PbSnTe have been used as infrared detectors and CdTe has been employed as a gamma ray detector and is also a promising candidate material for a thin-fUm solar ceU. 

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