Thin polycrystalline films of indium phosphide on low-cost substrates. Quarterly report No. 3, April 3--July 2, 1977

Abstract

The program is intended to develop the metalorganic chemical vapor deposition (MO-CVD) process for growth of InP films using triethylindium (TEI) and phosphine (PH/sub 3/) reactants in a H/sub 2/ carrier gas, and then to prepare such films on inexpensive substrate materials for subsequent fabrication of heterojunction polycrystalline solar cells by deposition of CdS (or other semiconductor) on the InP. Minor changes in reactor design have permitted achievement of InP film growth rates up to four times larger than those previously obtained. Deposition conditions have been established for obtaining good-quality undoped n-type epitaxial InP films on single-crystal (111A) and (111B) InP substrates, and p-type Zn-doped epitaxial InP films have been produced on both GaAs and InP single-crystal substrates, with doping concentrations in the 10/sup 16/-10/sup 18/ cm/sup -3/ range. Experiments have continued on the growth of polycrystalline InP films on various low-cost substrates, including several glasses, metals and metal alloys, and intermediate layers of metals and semiconductors previously deposited on glass substrates; a wide range of InP film properties has been obtained in these studies, results of which are summarized. Experimental Schottky-barrier device structures, employing thin Au barrier layers, have been fabricated on p-type InP films prepared in various single-more » and multiple-layer configurations. Detailed characterization of the transport properties in both undoped n-type epitaxial InP films on GaAs : Cr and InP : Fe semi-insulating substrates and Zn-doped p-type epitaxial films on GaAs : Cr substrates is presented and discussed. The first heterojunction photovoltaic solar cell employing a vacuum-deposited n-type CdS film and an epitaxial p-type InP film grown by MO-CVD has been fabricated and characterized.« less