HETEROEPITAXY OF CDTE ON GAAS AND SILICON SUBSTRATES

CdTe can be grown directly by molecular beam epitaxy on substrates such as GaAs or silicon, which exhibit very large lattice mismatches of 14.6% and 19% respectively. The occurrence of dual epitaxy, which has been previously reported for growth on (100)GaAs, has also been found recently for growth on (211)GaAs. The (133)CdTe-(211)GaAs hetero-interface presents a smooth continuation of the tetrahedral bond network from GaAs to CdTe, which is not the case for the (211)CdTe-(211)GaAs interface. Single-domain, twin-free CdTe(111)B films are currently obtained on Si(100) surface where single atomic steps are dominant. The crystalline quality of CdTe/Si films has been dramatically improved as confirmed by X-ray diffraction, photoluminescence and electron microscopy investigations. The narrowest rocking curves obtained for as-grown epilayers are 70 arcsec for (133)CdTe/(211)GaAs, 50 arcsec for a flash-annealed (211)CdTe/(211)GaAs and 140 arcsec for (111)B CdTe/(100)Si. These results confirm that CdTe/GaAs and CdTe/Si composite substrates should be viewed as prime candidates to replace bulk CdTe substrates.