Date

January 1989

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Applied Physics

Institution

Oregon Graduate Center

Abstract

Hg[subscript 1-x]Cd[subscript x]Te is the material of choice for fabrication of infrared detectors in the 8-14 µm and 3-5 µm regions. Alternative approaches to growth and processing, and alternative Hg- Te based materials offer promise for easier fabrication, and possible superior performance of infrared detectors. An investigation was undertaken to study the application of laser processing techniques to several alternative Hg-Te materials and HgCdTe. Bulk growth of HgATe (A = Cd, Mn, Mg, Ca, Sr, Ba, Be[beryllium]) produced material for subsequent investigation. Samples were prepared and then underwent initial characterization including mass density measurements, X-ray measurements of lattice parameter, FTIR measurements of bandgap, Hall and resistivity measurements, and a novel surface measurement based on the Seebeck Effect giving information about carrier type, density and mobility. Representative samples were annealed in a mercury overpressure to reduce the density of mercury vacancies. Hall measurements done on samples tracked changes in electrical properties caused by these anneals. Samples were then exposed to a CW CO2 laser in a study giving mercury loss as a function of exposure time, and laser power. Mercury loss was measured directly using EDX techniques and indirectly using a reflectivity experiment detecting the onset of surface melting which corresponds to the onset of significant mercury loss. Samples attached to a LN2 stage and exposed to the laser for extended periods experienced electrically significant mercury diffusion laterally within the material. This relocation was measured qualitatively with the aforementioned Seebeck technique and is correlated with theoretical models of temperature rise during laser exposure, and to sample preparation procedures. Using data obtained from mercury loss and diffusion studies, a laser annealing procedure was developed for use on ion implanted samples of HgMnTe. Hall measurements were done before and after implantation and an improvement in the electrical properties of the implanted/annealed layer was documented. The materials investigated are finally compared with regard to lattice parameter, dE[subscript gap]/dx relationships, Hall data and reflectivity/mercury loss data. This information is compared against similar information obtained for HgCdTe and the relative strengths and weaknesses detailed.

Identifier

doi:10.6083/M4PC3090

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