InGaAs/GaAs Quantum Dots for 1.3 μm Applications

Zero-dimensional charge carrier localization in the active region of a semiconductor laser was predicted two decades ago to lead to improved device performance. Self-organized growth of quantum dots (QDs) has since then evolved into the decisive method for defect-free QD fabrication to realize such localization, and the first QD injection laser demonstrated the basic validity of previous predictions [1]. Much effort was subsequently spend to extend the emission wavelength of In(Ga)As QDs in GaAs matrix to the datacom range at 1.3 μm. The basic approach aims at decreasing the energy of the dot’s electronic ground state by lowering the hydrostatic strain exerted on the dot by the matrix. Model calculations proved that strain release induced by a thin InGaAs layer with a lower In content on top of the QDs significantly decreases the ground state energy [2]. Combination of such strain-reducing layer (SRL) with a similar, additional layer underneath the dots leads to the dot-in-a-well (DWELL) approach which was successfully applied using molecular beam epitaxy to fabricate GaAs-based QD devices emitting at 1.3 μm. QD devices reaching this target have been fabricated only very recently using metalorganic vapor phase epitaxy (MOVPE) with its scaling ability for mass production. In the presentation concepts for growing InGaAs dots for 1.3 μm emission are discussed and encouraging latest results are presented. We used tertiarybutylarsine as a favorable arsenic precursor [3] and an individual adjustment of growth parameters within the stack of active QDs in a laser [4]. PL is used as a monitor to identify critical growth parameters. Data indicate a crucial role of the V/III ratio applied during growth [5]. InGaAs/GaAs QDs with a strain-reducing layer grown using a low V/III ratio show a robust thermal stability. The good performance is promising to open a way for 1.3 μm device fabrication using metalorganic vapor phase epitaxy.