Academic Awards 2024 booklet

15 Improving heat dissipation in hex-SiGe nanowires using 2D hBN flakes Photonic integrated circuits (PICs) rely on using photons instead of electrons and promise significant improvements in speed and efficiency compared to current electronic circuits. The efficient implementation of these into everyday-use devices relies on making them compatible with the industry-standard material: silicon. A missing crucial component for silicon-based PICs is an optical amplifier. Researchers at the TU/e aim to create these from specially-grown hexagonal silicon-germanium nanowires; however, the nanowires currently overheat before reaching the desired operational regime (lasing). In my work, I investigated a novel method for cooling these nanowires using 2D hexagonal boron nitride (hBN) flakes. I experimentally demonstrated the feasibility of creating such structures in the lab. Optical measurements I performed on the samples I created involved exciting the nanowire with a laser and measuring the intensity of the emitted light. Figure 1 shows how samples with hBN flakes allowed the nanowires to reach higher fluences without heating up. Fabrication steps were corrected for, and Figure 2 illustrates how the improvement can indeed be attributed to the hBN. Thanks to enhanced heat dissipation, we excited the nanowires to higher fluences than previously possible for this material and some results found as part of this research aligned with previously theoretically predicted phenomena, which are elaborated upon in my thesis. Figure 1: The background-corrected intensity of measured light emitted from a nanowire plotted against the fluence (which is proportional to the power of the excitation laser). The yellow data corresponds to measurements from 8 nanowires which were simply on SiO 2 (reference category). The teal data corresponds to 8 nanowires on top of hBN flakes. The stars mark the first time we observed black-body emission in the measurement wavelength. The triangles indicate that no such emission was observed even at the highest excitation power used (limited by experimental setup). Figure 2: The percentage of nanowires observed to first emit black-body radiation at a given fluence per sample category. The black-body emission signifies significant heating up, often destroying the nanowire. This was marked by stars in Figure 1. There is a significant improvement coming from the usage of hBN flakes, with over 60% of nanowires never heating up so much as to emit black-body radiation in the measurement range. We used the blue category to correct for differences coming from sample fabrication, and surprisingly found these also lead to some improvement. 0 2 4 6 8 0 50 100 150 200 250 300 Background-corrected Intensity [counts/s] Fluence [mJ/cm 2 ] Swiped onto SiO 2 Stamp-transferred onto hBN 2 4 6 8 never 0 20 40 60 80 Percentageof nanowiresper category Fluence atwhich blackbody radiationwas first observed [mJ/cm 2 ] Swiped onto SiO 2 Swiped &Washed on SiO 2 Stamp-transferred onto hBN