Modeling Laterally-Contacted nipi-Diode Radioisotope Batteries

A framework for modeling the power generation of laterally-contacted n-type/intrinsic/p-type/intrinsic (nipi) diodes coupled with an alpha-particle radioisotope source is developed. The framework consists of two main parts, the alpha-particle energy deposition profile (ADEP) and a lumped parameter equivalent circuit model describing the nipi device operation. Experimental measurements are used to verify the ADEP modeling approach which determines the spatially varying energy deposited within the device. Using these results, nipi-diode radioisotope batteries are simulated and the effect of the number of junctions, the thickness of the junction, and the alpha-particle flux on output voltage and power are investigated. The modeling results indicate that a 1 cm² bi-layer device (consisting of one source and two adjacent nipi-diodes) with a source activity of 300 mCi can reach a power output of 2 mW, excluding radiation damage effects.