Characterization of Mid-Infrared Stealthy Hyperuniform Surfaces for Semiconductor Cooling Applications

Abstract

This thesis investigates the fabrication and characterization of mid-infrared (mid-IR) stealthy hyperuniform (SHU) surface patterns to enhance passive radiative cooling in semiconductor materials. SHU metamaterials combine the isotropy of disordered structures with crystal-like photonic band-gap behavior, enabling geometry-driven control of thermal emission without angular sensitivity. By engineering these patterns on Indium Phosphide (InP) substrates, this work strengthens radiative cooling pathways.

The project integrates two experimental components. First, angle-resolved Fourier-transform infrared (FTIR) spectroscopy measures reflectivity of SHU-patterned and unpatterned InP samples across multiple angles. Cross-normalized datasets enable direct comparison of emissivity, revealing a broad mid-IR resonance at ~700–730 cm^-1 (13.7–14.3 µm) unique to the SHU sample and independent of angle. The analysis yields delta epsilon approximately equals +0.07, corresponding to ~+29 W/m^2 additional radiative cooling power. Since emissivity for opaque materials follows 1-R, these measurements directly quantify emission enhancement. Second, a controlled thermal experiment compares cooling of SHU-patterned and unpatterned InP samples heated to ~80°C on Thorlabs HT10K heaters. Temperature is monitored via an embedded NTC thermistor and a FLIR C5 thermal camera. After correcting for an 8.9% thermal mass difference, surface data show the patterned sample cooler at all 14 time points, with a mean reduction of 1.29°C and a 1.16°C lower asymptotic temperature. Thermistor time constants remain statistically equivalent, reflecting indirect coupling and convection-dominated heat transfer.

By linking optical signatures to cooling performance, this work provides the first experimental demonstration of mid-IR emissivity enhancement and improved chip-surface cooling in a fabricated SHU-patterned InP device. Future work includes optimizing resonance within the atmospheric window, vacuum testing to isolate radiative effects, and extending the approach to other III-V semiconductors.