We describe GaAs‐based tunnel junctions that are compatible with photonic devices, including long‐wavelength vertical‐cavity surface‐emitting lasers and multi‐junction solar cells. Tunneling was enhanced with semimetallic ErAs nanoparticles, particularly when grown at reduced substrate temperatures. Additionally, we present the first direct measurement of the quality of III‐V layers grown above ErAs nanoparticles. Photoluminescence measurements indicate that III‐V material quality does not degrade when grown above ErAs nanoparticles, despite the mismatch in crystal structures. These findings validate these tunnel junctions as attractive candidates for GaAs‐based photonic devices (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)