CHEMICAL BEAM EPITAXY FOR HIGH-EFFICIENCY INP SOLAR-CELLS

The aim of this work is to develop thin InP solar cells for space appl ications from more mechanically resistant, lighter, and cheaper substr ates. In this paper we present the development of a p(+)/nn(+) solar c ell structure with a very thin emitter layer. A thin emitter helps to increase the collection of carriers generated by high energy incident photons from the solar spectrum. Moreover, the use of a p+/nn+ structu re should improve the radiation resistance of this already radiation r esistant technology. A remarkable improvement of high energy photo-res ponse is shown for these CBE-grown very thin emitter InP solar cells. The ability to obtain a very high p-type InP doping level by using CBE avoided the sheet resistance increase that degrades the I-V character istic even for emitters only 400 Angstrom thick. It is also shown that the photo-response of thin base layers is reduced, and that more than 2.4 mu m thick base layers are necessary for a better collection of n ear InP band gap photons. (C) 1998 Elsevier Science B.V. All rights re served.