Electroreflectance of ion-implanted GaAs

Abstract

A systematic investigation of the electrolyte electroreflectance of GaAs with implanted Be, Se, and Si ions has been made. Topographical maps of carrier concentration and of implant-dependent modifications of the lineshapes have been obtained. The fluences for the implanted samples ranged from ∼1013 to 1015 ions/cm2. Using the E0 and E1 peaks, the lineshape variations have been mapped for the low- as well as high-fluence samples. The evidence suggests that at high fluence the extreme structural damage, resulting from implantation, generates an amorphous layer which upon annealing recrystallizes by a mechanism similar to liquid phase epitaxy. Depending on the fluence of the implant, apparent peak shifts of as much as 80 meV have been observed. These are explained as definitely not due to gross changes in the E1 and E1+Δ1 transitions but rather either due to a modification of the simple parabolic band model or due to a definite folding of one of these structures with a third, probably of excitonic origin and analyzed here for the first time. Moreover, the study of GaAs with Be and Se implants proved that electroreflectance is an unusually sensitive tool for the study and characterization of inversion layers.