IMPACT OF NATIVE OXIDE ON NEAR-FIELD RADIATIVE HEAT FLUX MODULATION IN SILICON-BASED PHOTONIC P-N JUNCTION

Dynamic modulation of near-field radiative heat transfer (NFRHT) holds considerable promise for thermal management, and the recent proposed photonic p-n junction is demonstrated to be an ideal NFRHT modulation element. However, the silicon-based photonic p-n junction will be influenced by the native silicon oxide (SiO₂), which forms rapidly on the silicon surface when exposed to air, reaching a thickness limit of ~2 nm. In this work, the impact of native SiO₂ layer on NFRHT modulation in silicon-based photonic p-n junction is investigated. The modulation under applied voltage is primarily driven by the conversion of plasmon polaritons in p- and n-type silicon. The native SiO₂ layer supports surface phonon polaritons (SPhPs), introducing a stable, voltage-independent heat flow component that shifts the near-field radiation heat flux-voltage profile upward and reduces the switching ratio from an ideal 9.3 (without SiO₂) to 3.6. To mitigate the impact of SiO₂ layer, deposition of a dielectric layer on the silicon surface to isolate it from air was explored. Among these, diamond, which does not support SPhPs within the relevant frequency, achieves a switching ratio of 8.3, nearly matching the ideal case. These findings provide valuable insights for optimizing NFRHT modulation in near-field photonic devices and guiding future experimental designs.