Molecular beam epitaxial growth and rapid thermal annealing effect of digital-alloy (In0.53Ga0.47As)1-z(In0.52Al0.48As)z lattice-matched to InP for 1.3-1.55 μm multi-quantum wells

Optimum growth condition for digital-alloy InGaAlAs was investigated as a function of the InAlAs thickness (n) of (InGaAs)_m/(InAlAs)_n short-period superlattices (SPSs) in the range of 1-5 monolayers (MLs), where m/n was kept constant. For n=1-5 MLs, both higher (H) and lower (L) energy peaks are resolved. The H peak is from the excitonic transition, while the L is due to LO-phonon. It was found that n=2 MLs is most suitable for digital-alloy InGaAlAs. Digital-alloy InGaAlAs for 1.55 μm. MQWs shows narrower linewidth at 10 K-PL (5.7 meV) than that of analog-alloy InGaAs/In(Ga)AlAs MQWs grown by other state-of-the-art growth method. Rapid thermal annealing effect of 1.3 μm digital-alloy InGaAlAs MQW structure on optical and structural properties was investigated with 300 K-PL and transmission electron microscopy. 300 K-PL peak intensity rose drastically above the annealing temperature (T_RTA) of 625°C, which increased up to ∼333 times larger than that of as-grown sample without any significant shift of the PL peak wavelength. This extraordinary increase of the PL peak intensity above T_RTA=625°C is attributed to the curing of nonradiative centers mainly in InAlAs grown at lower temperature than its congruent temperature, and partially at the heterointerfaces between InGaAs/InAlAs SPSs.