Influence of As 4/Ga flux ratio on Be incorporation in heavily doped GaAs grown by molecular beam epitaxy

Abstract

The Be incorporation and diffusion in heavily doped MBE grown GaAs epilayers has been studied. By varying the As 4/Ga flux ratio, substancial changes in the Be incorporation mechanism and diffusion coefficient have been observed. The measurement Be SIMS profile with a higher flux ratio ( R = 32) is almost the same as the designed profile (i.e., almost no diffusion of Be). However, at a lower flux ratio ( R = 20) the profile is significantly different from the designed structure. This behavior is difficult to explain by any conventional interstitial substitutional diffusion models. When the flux ratio was increased from 27 to 32, a sudden change in the Be distribution pattern and a rapid decrease in Be diffusion coefficient were observed. This strong dependency of Be incorporation and diffusion with the As 4/Ga flux ratio will be discussed in connection with previously proposed surface state pinning model.