Electrical activation of Te and Se in GaAs at extremely heavy doping up to5 x 10(20) cm(-3) prepared by intermittent injection of TEG/AsH3 in ultra-high vacuum

Doping characteristics of group VT elements (Te and Se) on (100)-oriented G aAs are investigated at an extremely heavy doping level up to 5 x 10(20) cm (-3) on the basis of the surface stoichiometry control to improve the incor poration of impurities. By changing the gas injection sequences, the surfac e stoichiometry before the introduction of impurity precursors is controlle d. The impurity concentration is measured by secondary ion mass spectroscop y (SIMS) analysis and the activation ratio is determined in conjunction wit h the results of Hall effect measurements. It is shown that the incorporati on of Te and Se is extremely enhanced when DETe and DESe are exposed on the Ga-stabilized surface. From the electrical measurements and SIMS results, the segregation of defects due to doped impurity atoms is strongly suggeste d. The defect formation mechanism of heavily impurity doped GaAs is discuss ed in view of the formation of impurity-defect complex and the control of s ite-occupation of doped impurities. (C) 2000 Elsevier Science B.V. All righ ts reserved.