Determination of Shockley - Read trap parameters in n- and p-type epitaxial

Abstract

Determination of the origin of Shockley - Read traps in (CMT) is of great importance if the quality of infrared detectors made in this material is to be improved. Work has been carried out to develop a model enabling the determination of both the density and position of traps and their possible nature, i.e. acceptor, donor or neutral. Initial comparisons were made with a published model which enabled the trap density and capture rates to be obtained. This was then extended to estimate the trap position. This approach has been used, for the first time, to investigate both n- and p-type layers grown by metal-organic vapour phase epitaxial (MOVPE) techniques. Both vacancy controlled and impurity doped samples have been considered. The results showed that for p-type CMT layers the trap was predominantly at a mid-gap position with trap densities increasing with hole concentration. This leads to the conclusion that the trap in p-type epitaxial material may be associated with the metal vacancy. In n-type CMT layers the effects of trapping were considerably reduced.