Nanowire betavoltaic nuclear battery

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Betavoltaic devices use energetic electrons (beta particles) to create electron-hole pairs in a semiconductor byimpact ionization for direct generation of electrical power. Betavoltaics provide compact, long-life, and highenergy density devices for nanowatt to microwatt applications such as mobile electronic devices, implantablemedical devices, and autonomous wireless sensor networks. The implementation of betavoltaics is presentlylimited by their relatively low efficiency (<10%). We propose to fabricate gallium phosphide (GaP) nanowireson Si substrates by the self-assisted growth method. The high bandgap of GaP nanowires will offer a highlimiting efficiency of about 25% and a reduced cost by growth on inexpensive Si substrates. The beta source(Ni-63) will be embedded in the space between nanowires, using a sol-gel spin-coating technique recentlydeveloped by the applicant. In this way, the beta source will be nearly completely surrounded by semiconductormaterial, improving the capture efficiency of emitted beta particles and using only a fraction of thesemiconductor volume of existing technology.