Thermal acceptors in germanium

Diffusion Mechanisms and Point Defects in Silicon and Germanium

“…Within this restriction, the estimates hold for all diffusion mechanisms ; they are necessarily somewhat more conservative than the estimates [ll] based specifically on a monovacancy mechanism (for Ge : C1v (T,) > 1. 5 x An upper limit for Ceq( T) may be obtained as follows: Irrespective of whether self-diffusion occurs by a defect mechanism or not, the contribution t o the self-diffusion coefficient calculated for any self-diffusion mechanism X from the defect properties (energies and entropies of formation and migration, correlation factors etc.) must be less than (if other mechanisms contribute also) or equal t o the experimental value exDsD of the self-diffusion coefficient, i.e.,…”

“…It must be concluded that most of the earlier quenching experiments give no informations a t all on intrinsic defects in germanium but should be rather interpreted in terms of impurities. A brief survey of these papers up to 1956 has been given by Letaw [5], to whose paper the reader is referred for further details.…”

“…On annealing quenched samples between 400 and 520 "C, an initial increase in hole concentration was observed by Mayburg [167] when measurements were made at -78 "C. This rise was not observed if the hole concentration was measured a t room temperature. Letaw [5] proposed a model t o explain this phenomenon as due to formation of divacancies and large clusters, basing this on a monovacancy migration energy of -1 eV. In view of the evidences for a high monovacancy mobility the model appears now incorrect.…”

“…Considerable effort has gone into the identification of these "thermal acceptors". (For a review of this work up t o 1956 see Letaw [ 5 ] . ) Van der Maesen et al [S] found that after heat treatment a t 800 "C copper impurities in Ge act as acceptors.…”

A Controlled Diffusion Process for Indium in N-Type Germanium

“…Copper is apparently usually present in trace amounts on the surface and, due to its very high diffusivity at elevated temperatures, spreads rapidly throughout the bulk of the germanium where it acts as an acceptor center (2,3). In addition, quenches from high temperatures may introduce acceptor levels of another kind, which are apparently due to quenched-in lattice defects (4,5). Except with very rapid cooling rates, however, this latter type of thermal acceptor is not too troublesome.…”