Molecular beam epitaxy of CdSexTe1-x photovoltaic junctions on silicon substrates

The II–VI semiconductor cadmium selenide telluride CdSeTe was grown by MBE on silicon. The large lattice mismatch to the silicon was accommodated in smaller steps using a beryllium telluride - zinc telluride buffer layer. A CdTe film grown on this buffer had about three times narrower x-ray diffraction peak than a CdSe0.40Te0.60 alloy. Photojunction devices were formed into mesa structures with n⁺Si / p⁺BeTe p-type bottom contacts and n-type CdSe top emitter layers, with thin (≪1 μm) CdSeTe base layers. The photocurrent of junctions with CdTe base layers was about an order of magnitude greater than those with the CdSe0.40Te0.60 alloy, most likely due to short minority carrier lifetime in the ternary.