Abstract

Epitaxial Distributed Bragg Reflector (DBR) structures are a constituent part of many optoelectronic devices, for example, in Vertical- Cavity Surface-Emitting Lasers (VCSELs). For a laser emission at λδ=980™ 1000 vm, the binary GaAs/AIAs combination provides an adequate choice, considering the thermal conductivity and the refractive index step. However, in this case, the potential barriers at the hetero-interfaces, particularly in the p-type doped DBRs, impede the current flow and lead to high series resistance. To our knowledge, little attention has been given to the fact that, in MBE at the commonly used growth temperature (T_sub) of 580 – 620°C, a strong outdiffusion of Be from the AIAs is observed,^1,2 which, in a DBR structure, will additionally increase the series resistance. In this paper, we present for the first time a detailed study of the diffusion of Be in GaAs/AIAs DBR structures, based on SIMS as well as electrochemical C-V measurements. We demonstrate that, when a lower T_sub is chosen, the outdiffusion vanishes, which finally allows the implementation of δ-doped transition layers in order to reduce the series resistance drastically.

© 1993 Optical Society of America