ELECTRON-MOBILITY IN P-TYPE EPITAXIALLY GROWN HG1-XCDXTE

The electron minority carrier mobility is an important parameter because of its effect on the diffusion length for determining the performance of semiconductor infrared detectors. The suppression of the diffusion current of a photodiode with magnetic field has been used to determine the electron mobility in epitaxially grown p-type Hg1-xCdxTe (CMT). This technique enables the mobility to be measured in the active region of a photodiode. Results have been obtained as a function of temperature for material covering a wide range of acceptor concentrations from 2 x 10(15) cm-3 to 2 x 10(17) cm-3. The mobility in the more highly doped samples is considerably lower than is found in low-doped n-type material and this can largely be accounted for by ionized impurity scattering. A semi-empirical formula is derived and is shown to give reasonable agreement with the experimental results. The deduced mobility can be combined with a measurement of the diffusion length to calculate the effective minority carrier lifetime in the active region of the diode. This has been compared with the lifetime measured by photoconductive decay in separate samples of the same material.