THE INCORPORATION OF ERBIUM INTO MOLECULAR-BEAM EPITAXY-GROWN GALLIUM-ARSENIDE

Erbium-doped gallium arsenide has been grown by molecular beam epitaxy under varying growth conditions and analysed by secondary ion mass sp ectrometry. The concentration of erbium incorporated into the gallium arsenide lattice for a given effusion cell temperature has been found to vary considerably with the V : III (As : Ga) flux ratio. Higher lev els of erbium incorporation occur when growth takes place close to sto ichiometry rather than under arsenic rich conditions. This behaviour h as been observed for erbium concentrations between 10(16) and 5 x 10(1 9) cm(-3). SIMS data show the existence of an erbium-rich surface laye r which, in the presence of unintentional impurities, is incorporated into the GaAs at an enhanced rate forming an unusual doping spike.