Electron mobility in p-type epitaxially grown CdxHg1-xTe

The minority carrier mobility is one of the fundamental material properties affecting the performance of CdxHg1-xTe detectors. It is also required directly to determine the steady state lifetime, which, when used in conjunction with the lifetime from transient photoconductive decay measurements, can lead to information on Shockley-Read traps. The measurement of electron mobility in p-type material is not straightforward and many different approaches have been tried. Our work has concentrated on developing a model to predict the electron mobility in p-type CdxHg1-xTe. Two approaches have been considered. Firstly, the electron to hole mobility ratio (b) was investigated and secondly further work was carried out using the semiempirical formula developed in a previous study. It was found that at temperatures above 200 K there was very little difference between the electron mobility in epitaxial p-type CdxHg1-xTe layers and that measured directly in n-type layers and good fits were obtained whichever method was used. At lower temperatures the model developed in our previous study was seen to give the most consistent results, although introducing variations in b with temperature led to improvements in the constant-b model below 200 K. The predicted values have been used to determine the steady state lifetime.