Advanced Methods of Semiconductor Research Seminar – Tuesday 12 of May 2026
We cordially invite you to Advanced Methods of Semiconductor Research Seminar on Tuesday 12 of May 2026 at 13:15 in room 321, building A-1, where there will be delivered a lecture:
Control of areal density and emission wavelength of MOVPE-grown InAs/InP quantum dots
by Jan Śmigiel
from Department of Experimental Physics, Wrocław Tech
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Lecture abstract:
Self-assembled InAs/InP quantum dots (QDs) have attracted considerable attention as these nanoscale objects provide effective, quasi-zero-dimensional confinement for charge carriers. This results in exciton formation and photon emission via radiative recombination in the short-wave infrared range, possibly overlapping the O- and C-telecom bands (1300 nm and 1550 nm). These dots are typically nucleated via the Stranski–Krastanov (SK) growth mode, driven by strain relaxation between the InP barrier and the InAs material. While standard SK growth yields surface densities of approximately 10^11 cm^(-2) – ideal for laser gain media—this work focuses on the low-density regime (<10^9 cm^(-2)), which is essential for developing efficient single-photon sources (SPS). We demonstrate precise control over QD nucleation by tailoring precursor flow rates, temperature, and growth time, thereby modulating surface density, morphology, and emission wavelength. The structures were grown in an AIXTRON CCS 3×2” MOVPE reactor using H2 carrier gas with AsH3, PH3, and TMIn precursors. Initially, a 200 nm InP buffer was deposited on InP (001) at 645 °C. The temperature was subsequently ramped down to 510 °C and stabilized. Following the introduction of AsH3 flow, QDs were nucleated upon opening the TMIn valve. The nanostructures were then overgrown with a 200 nm InP cap, during which the temperature was gradually increased to 600°C over the first 110 nm. Finally, a second QD layer was deposited on the surface under identical conditions for AFM characterization. By adjusting growth parameters, we tuned the QD density across three orders of magnitude (10^7 to 10^10 cm^(-2)). The initial emission of the low-density ensemble was centered above 1800 nm. However, by introducing PH3 flux during growth – facilitating phosphorus incorporation into the lattice – the emission was shifted closer to the desired spectral range while maintaining previous morphology and density of QDs. The high optical quality of these nanostructures was preliminarily verified via photoluminescence imaging, resolving individual bright QDs in third telecom window. Ongoing research focuses on integrating these QD structures with InP-based Distributed Bragg Reflectors (DBRs). Various material approaches are being evaluated to enhance photon collection efficiency, a critical requirement for advanced SPS-based devices.
