Molecular beam epitaxial growth of CdTe and related Ⅱ-Ⅵ materials on Si for the fabrication of infrared detectors and solar cells

摘要

CdTe/Si substrates with etch-pit densities ~5 ×10~4 - 2 ×10~5 cm~(-2) and x-ray diffraction full-width at half-maximum <60 arcsec over >60% of a 3" substrate and ≤85 arcsec over the entire area are now available. Midwave and shortwave HgCdTe infrared detectors fabricated on these substrates have device characteristics as good as those of detectors fabricated on lattice-matched CdZnTe substrates. Also, minority carrier lifetimes of 100s of nanoseconds are measured for CdTe/Si and CdZnTe/Si, and both can be p-doped 10~(17) cm~(-3) and n-doped >10~(20) cm~(-3). Calculations suggest that the use of these materials should yield multijunction solar cells with efficiencies higher than those of the corresponding Ⅲ-Ⅴ multijunction cells at much lower cost, using rugged, large-area, inexpensive active Si substrates. The first CdZnTe/Si single-junction solar cells fabricated by EPIR displayed an electronic-charge times open-circuit voltage, qV_(oc), within ～0.45 eV of the CdZnTe bandgap E_g, as good a result as that for the best Ⅲ-Ⅴ alloy single-junction cells, and confirmed the suitability of single-crystal CdZnTe/Si for the manufacture of high-efficiency solar cells.