COMPARISON OF SI DELTA-DOPING WITH HOMOGENEOUS DOPING IN GAAS

Homogeneous and delta-doped GaAs:Si, has been grown by molecular beam epitaxy at growth temperatures between 410 and 660-degrees-C. The doping density varied from 1 X 10(18) to 1.5 X 10(20) CM-3 and from 1 X 10(12) to 7 X 10(13) cm-2 for the homogeneously and delta-doped GaAs, respectively. For homogeneous doping at 410-degrees-C, the maximum carrier concentration is 1.9 X 10(19) cm-3, while at 660-degrees-C it is only 7.4 X 10(18) cm-3. In contrast, for the 8-doping the highest maximum sheet carrier concentration of 2.5 X 10(13) cm-2 is found at a growth temperature of 660-degrees-C, whereas at a growth temperature of 410-degrees-C the maximum sheet carrier concentration is only 5 X 10(12) cm-2. We attribute the increasing maximum sheet carrier concentration of the delta-doped samples with growth temperature to the increasing width of the doping spike due to segregation of the Si-atoms in GaAs. Assuming that the incorporation of the segregated atoms and the homogeneously doped atoms is similar, we have determined the width of the dopant distribution by comparing the results of our homogeneously and delta-doped samples for a given growth temperature. The width of the delta-doping distribution is found to increase both with growth temperature (480-660-degrees-C) and doping density. No concentration dependent doping width is found for the lowest growth temperature of 410-degrees-C. The results were confirmed by SIMS analysis.