MINORITY-CARRIER LIFETIME IN DOPED AND UNDOPED EPITAXIALLY GROWN N-TYPE CDXHG1-XTE

The performance of infrared detectors made from CdxHg1-xTe (CMT) is re lated to the lifetime of minority carriers in the material. Both photo conductive and photovoltaic devices require long lifetimes for high pe rformance. This paper compares lifetime measurements on epitaxially gr own CMT layers which have been isothermally annealed to minimize the v acancy concentration and are n-type due to native defects, residual im purities, or deliberately added dopants. Layers grown by liquid phase epitaxy (LPE), metalorganic vapor phase epitaxy (MOVPE), and molecular beam epitaxy (MBE) have been considered, in all cases the same measur ement system was used under the same low injection conditions. All lay ers were of compositions required for operation in the 8 to 14 mu m wa velength range. Comparisons have been made between undoped and indium doped LPE layers and undoped and iodine doped MOVPE layers. It was hop ed that a deliberately introduced donor impurity would give better con trol of the n-type properties. The effect of passivation on the measur ement of lifetime has also been considered, the results showing that a surface with a native oxide is required to obtain the true bulk lifet ime as has been seen previously for bulk material.