EFFECT OF AS PRESSURE ON SE DELTA-DOPED IN GAAS BY MOLECULAR-BEAM EPITAXY

Using elementary Se as an n-type dopant, Se delta-doped GaAs films were grown on (001) GaAs substrates by molecular beam epitaxy. The results of secondary ion mass spectroscopy and capacitance-voltage measurement show that it is necessary to use adequate As pressure during Se deposition to form a sharp interface. The Se concentration in the films did not change monotonically and reached a maximum value followed by a minimum value as a function of Se deposition time. The Se incorporation rate decrease over long Se deposition time is probably caused by Se condensation on the surface to form more volatile molecules. A possible model of the Se-adsorbed surface is proposed by considering the reflection high-energy electron diffraction patterns.