STRAIN COMPENSATION IN HIGHLY CARBON-DOPED GAAS ALAS DISTRIBUTED BRAGG REFLECTORS/

We use molecular beam epitaxial growth in order to synthesize strain c ompensated GaAs/AlAs-based distributed Bragg reflectors (DBR). The str ain compensation is achieved by introducing carbon doping up to densit ies of about 2 x 10(20) cm(-3). The residual strain with respect to th e GaAs substrate can be reduced to less than 1 x 10(-4). X-ray topogra phs of the strain compensated DBRs showed no misfit dislocations, thus proving that the critical thickness for the formation of dislocations in strain compensated DBRs is much larger than in the undoped and Be- doped cases. X-ray reciprocal space mapping reveals a structural degra dation of the DBR:C for thicknesses above 2.5 mu m and the defect dens ity is found to be much lower in AlAs:C than in GaAs:C. We study the e ffect of the strain compensation on the morphology and the optical ref lectivity of the DBRs.