Comparison of Zn and Mg incorporation in MOVPE InP/GaInAsP laser structures

The incorporation processes of Zn and Mg in InP and related ternary and quaternary layers for long wavelength laser applications are compared. It is shown that in InP above a critical concentration of (1-2)×10¹⁸ cm^-3 a sudden onset of dopant diffusion during growth is observed for Zn and Mg. This diffusion during growth can be markedly reduced by counter-doping with Si (Fermi level effect). Below the critical concentration Zn dopant profiles exhibit the same steep flanks as Mg dopant profiles suggesting the same low diffusion coefficients. Zn appears to be more suitable for p-type doping of InP, GaInAs, and GaInAsP, because accurate control of the dopant level in the epitaxial layers is easier to achieve with Zn than with Mg