Light Trapping in Photonic Power Converters with Nanotextured III–V Window Layers

A III–V semiconductor nanofabrication process is developed for narrow‐band photovoltaic devices, i.e., photonic power converters (PPCs). PPCs can benefit strongly from light trapping because their narrow‐band illumination allows optical resonances to be tuned to the incident wavelength and angle, enabling stronger absorption enhancement than is typically achievable under broadband solar illumination. In this work, the finite‐difference time‐domain (FDTD) method is used to identify designs that achieve strong near‐bandgap resonances and high absorptance in ultrathin III–V absorbers, demonstrating that periodic nanostructures can exceed classical isotropic‐scattering limits. Parameter sensitivity is evaluated, and strategies to improve fabrication tolerance are identified. Finally, experimental nanostructured surfaces are fabricated using electron‐beam lithography and Cl 2 /Ar plasma etching to create dense microscale features with nanoscale gaps. The impact of the window‐layer nanofabrication on absorber‐layer minority‐carrier lifetime is characterized with time‐resolved photoluminescence (TRPL). TRPL measurements indicate that the nanotextured material initially exhibits a similar lifetime to the planar reference, but its lifetime decreases over subsequent months, motivating the use of passivation treatments in future studies. These findings demonstrate the potential of front‐surface nanotexturing for enhancing absorption in III–V PPCs and provide design guidance for light‐trapping performance, fabrication tolerance, and surface passivation in thin photovoltaic devices.