Visible electroluminescence from porous silicon np heterojunction diodes

We report the preparation of silicon-based visible light-emitting diodes, configured as heterojunctions between porous silicon (formed by electrochemical etching of p-type silicon wafers), and n-type indium tin oxide (ITO). The transparent ITO film allows light emission through the top surface of the device, under a forward electrical bias of several volts across the junction. Photogenerated currents are observed under reverse biases. A tentative model for this electroluminescence is presented, based on injection of minority carriers through a narrow interphase region into the porous silicon structure, where radiative recombination occurs.