The observation of oscillations in secondary electron emission during the growth of GaAs by MBE

Abstract The use of RHEED oscillations to determine growth rates and alloy compositions in MBE film growth is now in widespread use. Similar oscillations have also been observed in the intensity of the absorbed current at the substrate. We report here the first observation of intensity oscillations in the secondary electron emission from the substrate during the growth of GaAs and AlAs by MBE. The apparatus used in these experiments consisted of the RHEED gun mounted in its conventional position in the MBE growth chamber and a secondary electron detector mounted in one of the effusion cell ports. The RHEED beam was positioned on the sample as would be done for normal viewing of the diffraction pattern. Upon the initiation of film growth, oscillations in secondary electron intensity were observed with a decay envelope very similar to that observed for RHEED oscillations and were sustained for as long as 5.5 min or about 220 cycles. Oscillation frequency varied with the Ga or Al oven temperature and was synchronous with the RHEED oscillations. This technique offers the possibility of monitoring monolayer oscillations for use in establishing growths rates with a relatively simple in situ detector.