Minority Carrier Lifetime in Doped and Undoped Epitaxially Grown n-type Cd_xHg_(1-x)Te

摘要

The performance of infrared detectors made from Cd_xHg_(1-x)Te (CMT) is related to the lifetime of minority carriers in the material. Both photoconductive and photovoltaic devices require long lifetimes for high performance. This paper compares lifetime measurements on epitaxially grown CMT layers which have been isothermally annealed to minimize the vacancy concentration and are n-type due to native defects, residual impurities, 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 measurement system was used under the same low injection conditions. All layers were of compositions required for operation in the 8 to 14 μm wavelength range. Comparisons have been made between undoped and indium doped LPE layers and undoped and iodine doped MOVPE layers. It was hoped that a deliberately introduced donor impurity would give better control of the n-type properties. The effect of passivation on the measurement of lifetime has also been considered, the results showing that a surface with a native oxide is required to obtain the true bulk lifetime as has been seen previously for bulk material.