This technology relates to neutron-detecting structures and methods of fabrication. Efficient solid-state neutron-detectors with large detecting surfaces and low gamma sensitivity are desired for detecting and preventing proliferation of special nuclear materials (SNMs). Unfortunately, available neutron-detectors are limited, for instance, by size, weight, high bias voltage requirements, andor cost due, for instance, to limited supply of enriched helium (3He) gas, which is currently employed in most neutron-detectors. This technology provides a structure with a substrate including cavities extending into the substrate; a p-n junction within the substrate and a neutron-responsive material disposed within the cavities. The neutron-responsive material is responsive to neutrons absorbed and releases ionizing radiation reaction products. The p-n junction within the substrate extends along the inner cavity walls of the substrate reduces leakage current of the neutron-detecting structure.