The effect of the transition energy of 3-donor clusters on far infra-red absorption in n-type semiconductor materials was investigated by means of a multi-configurational self-consistent-field model calculation. It was shown that it was essential to consider the many-particle correlation effects within 3-donor clusters. When electron correlation was taken into account, the present results supported the interpretation of an unidentified peak energy as being due to electronic transitions in these clusters. The suggestion that the X-line in GaAs arose from such transitions was confirmed.

Optical Properties of Donor-Triad Cluster in GaAs and GaN. J.Souza de Almeida, A.J.da Silva, P.Norman, C.Persson, R.Ahuja, A.Ferreira da Silva: Applied Physics Letters, 2002, 81[17], 3158-60