Photovoltaic device formed on porous silicon isolation

Abstract

A photovoltaic device includes lateral P-I-N light-sensitive diodes disposed on a silicon island formed by a P− epitaxial layer and surrounded by trenches that provide lateral isolation, where the island is separated from the substrate by a porous silicon region that is grown under the island and isolates the lower portions of the photovoltaic device from the highly doped substrate. The trenches extend through the P− epitaxial material into the P+ substrate to facilitate self-limiting porous silicon formation at the bottom of the island, and also to suppress electron-hole recombination. A protective layer (e.g., SiN) is formed on the trench walls to further restrict porous silicon formation to the bottom of the island. Black silicon on the trench walls enhances light capture. The photovoltaic devices form low-cost embedded photovoltaic arrays on CMOS IC devices, or are separated to produce low-cost, HV solar arrays for solar energy sources, e.g. for solar concentrators.