Electron transport to positive centers in GaAs

The origin of neutral muonium defect centers in semi-insulating GaAs has be en studied using muon spin rotation/relaxation techniques employing alterna ting electric fields. This technique prevents the accumulation of near-surf ace charges which may screen the external field. Suppression of the bond-ce ntered muonium signal with electric field suggests that muonium formation p roceeds via transport of excess electrons from the ionization track to the muon. The characteristic field of about 5 kV/cm may correspond to an electr ic field induced ionization of the muon donor impurity center. (C) 1999 Pub lished by Elsevier Science B.V. All rights reserved.