Suppression of thermal atomic interdiffusion in InGaAs/AlGaAs QW laser structures

Abstract

Titanium dioxide (TiO 2 ) cap layers were deposited onto C-doped InGaAs/AlGaAs QW laser structures by electron-beam evaporation in order to investigate their effect on atomic interdiffusion. In comparison to the as-grown sample, a negligible shift of the photoluminescence peak was observed after annealing at 900 o C, indicating that the atomic interdiffusion was greatly suppressed by TiO 2 capping layers. For the uncapped sample, the high temperature annealing step significantly improves the threshold current density in laser diode devices but leaves the internal efficiency unchanged. We attribute these effects to the activation of the carbon p-type dopant, as demonstrated by electrochemical C-V capacitance-voltage and X-ray measurements. SIMS analysis shows that the carbon atomic profile does not significantly change after annealing. In contrast, a similar Zn doped laser structure shows an almost flat Zn profile after annealing at 925 0 C, due to considerable indiffusion from the highly doped p ++ GaAs top contact layer into the rest of the structure.

A Comparison of Zinc and Carbon Doped on the Atomic Interdiffusion of InGaAs/AlGaAs Quantum Wells Laser Structures After Annealing

“…Annealing at 900 o C increased the electrically active carrier concentration in the top p ++ GaAs layers and the AlGaAs cladding layers by about 29% and by 58%, respectively. The increase of carrier concentration in the carbon doped sample is due to the removal of the C-C interstitial pairs that have been reported previously 12) .…”