METALORGANIC CHEMICAL-VAPOR-DEPOSITION GROWTH OF INN FOR INN/SI TANDEM SOLAR-CELL

A new tandem solar cell having an InN top cell is proposed since InN is a binary material having a bandgap of about 1.9 eV suitable for a top cell in a 2-junction tandem cell. An estimation of the conversion efficiency of InN/Si tandem cell has been made. For a 2-terminal cell, the bandgap of InN, 1.95 eV, is close to the optimum for AM 0 illumination because currents between top and bottom cells can be matched. The MOCVD growth of InN has been studied as a key technology for device fabrication. Epitaxial growth of InN directly on Si using the MOCVD technique is unsuccessful because of the formation of an amorphous SiN, layer on the Si substrate surface. Characterization has been made for single-crystalline InN films grown on alpha-Al2O3 substrates. Compared with InN films grown at a reduced pressure (similar to 76 Torr), those grown at the atmospheric pressure have a lower background carrier concentration and a higher electron mobility, although their surface morphology and crystallographic quality are somewhat worse.