Continuous p-n junction with extremely low leakage current for micro- structured solid-state neutron detector applications

Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as B and LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p-n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p-n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p-Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p-n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm size were studied. A very low leakage current density of ~2×10 A/cm at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p-n junction.