Influence of impurity-free vacancy diffusion on the optical and optoelectronic properties of the In_0.53Ga_0.47As/In _0.52Al_0.48As multiple quantum wells electroabsorption modulator structure

The effects of impurity-free vacancy diffusion using a SiO₂ capping layer on the optical and optoelectronic properties of the In _0.53Ga_0.47As/In_0.52Al_0.48As multiple quantum wells (MQW) electroabsorption (EA) modulator structure are investigated. A significant improvement (about 20 times compared to an as-grown sample) of photoluminescence (PL) intensity was observed after thermal treatments at temperatures of above 700 °C. In this structure, however, a red shift was observed after rapid thermal annealing (RTA) using the SiO ₂ capping layer, in contrast to the blue shift in conventional interdiffused MQW. A red shift of about 27 meV was obtained at an annealing temperature of 800 °C for 45 s without noticeable PL linewidth broadening. We believe that the red shift is attributed to the exchange between Ga of an InGaAs well and In of an InAlAs barrier. InGaAs/InAlAs MQW EA modulators were fabricated on as-grown and annealed substrates. The basic characteristics of the devices fabricated before and after RTA were evaluated by current-voltage and photocurrent measurements.