STOICHIOMETRY OF MELT-GROWN N-TYPE GaAs AS REVEALED BY PHOTOLUMINESCENCE MEASUREMENTS

A comparative study of the 77K PL spectra of n-type GaAs single crystals, grown by the horizontal or Czochralski technique, shows that the former are crystallized from Ga-rich melts (although in equilibrium with 1 atm As-pressure) whereas the latter are pulled from As-rich melts (although the starting loads are mostly As-deficient). Besides the VGa, copper appears as the major compensating acceptor in these crystals. Association of Cu and/or VGa with VAs and/or donor atoms tends to neutralize this compensation. This work shows how the above interaction explains the empirically determined relation ND∝(ND-NA), which is shown to hold for crystals of various sources.