Blocking of photoconductor surfaces by thin graded-gap layers as technique to serious improvement of excess charge carrier excitation efficiency



Excitation efficiency (η) of excess electron-hole pairs in semiconductor body is one of key parameters determining performance of semiconductor radiation detectors. Designers and producers of semiconductor radiation detectors are interested in effective affordable techniques that improve excitation efficiency seriously. We present general consideration of perspective technique based on model structure consisting of homogenous absorber layer with fixed value of energy gap and two thin graded-gap layers blocking absorber layer from front and back sides. Calculations of η were performed with assumptions: interfaces are electrically neutral; density of recombination centres at interfaces is negligible and value of graded-gap field at interfaces is changed abruptly to zero. It was shown that η could be sufficiently high even at infinite surface recombination rate on outer surfaces of the structure, it is important to note that big gradient of energy gap in graded-gap layers is not required in this case. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)