The doping behavior of indium and iodine have been investigated for mercury cadmium telluride (MCT, Hg1−xCdxTe ) layers deposited by the interdiffused multilayer process procedure at 400 °C using diethyl tellurium and dimethyl cadmium. Trimethyl indium and solid iodine were used as dopant sources. Both elements exhibited donor behavior under the conditions employed. Secondary ion mass spectrometry profile analysis was used to demonstrate that indium required a relatively long period during growth to attain an equilibrium concentration in the layer; in addition a significant reactor system memory was observed allied to a relatively fast diffusion rate. Iodine showed encouraging dopant properties at low concentration levels, the chemical concentration of iodine was in good agreement with the free donor level from Hall measurements. The advantage and applicability of each of the three chemical analysis procedures used in this work are discussed together with comments on the residual impurity content and electrical properties of undoped layers.
Thin layer semiconductor materials are analysed, by raster scanning the sample surface under a focused Q-switched Nd-YAG laser beam, in the source chamber of a high resolution MS702 mass spectrometer. The positive ions produced by the laser plasma erosion give a complete impurity survey of the layer down to detection limits of approximately 0.001 ppm atomic. Results have shown that surface impurities are effectively removed in the first scan and subsequent scans over the same area have given true measurements of impurities in typical layers.The method gives automatic erosion of sample surface areas from 0.1-130 mm2 with ionisation and mass analysis of the sample material removed. The depth of penetration is dependent on the material being analysed and the laser beam power at the sample surface. In general it is variable between 0.2 and 4 pm for each scan. Any material, including insulators, can be analysed by this method providing it is not completely transparent to the laser light.
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