HALL-EFFECT CHARACTERIZATION OF SILICON ACTIVATION AND SEGREGATION INPLANAR-DOPED GAAS-ALAS SUPERLATTICES

We have analyzed Hall data in GaAs-AlAs superlattices grown by molecul ar beam epitaxy. All samples had a very short period (3.7 nm) and were planar doped with silicon at a sheet density of 3.3 X 10(10) cm(-2) p er plane. Silicon was introduced selectively either in the GaAs layers , in the AlAs layers, or at the interface. The silicon electrical acti vation did not depend on the doping plane location. Conversely, the th ermal activation energy of the Hall carrier concentration was found to depend strongly on the doping plane location. From our experimental r esults, we estimate the silicon segregation length to be lower than 1. 5 nm at a growth temperature of 550 degrees C. (C) 1995 American Insti tute of Physics.