Erbium in crystal silicon: Optical activation, excitation, and concentration limits

The optical activation, excitation, and concentration limits of erbium in crystal Si are studied. Preamorphized surface layers of Czochralski-grown (Cz) Si(lOO), containing 1.7X lOI O/cm3, were implanted with 250 keV Er at Auences in the range 8X lo”--8X lOI cm-‘. After thermal solid-phase epitaxy of the Er-doped amorphous layers at 600 “C, Er is trapped in the crystal at concentrations ranging from 3 X lOI to 7X1019 Er/cm3, as measured by secondary-ion-mass spectrometry. Photoluminescence spectra taken at 77 K show the characteristic Ers+ intra-4f luminescence at 1.54 pm. Photoluminescence excitation spectroscopy shows that Er is excited through a photocarrier-mediated process, Rapid thermal annealing at 1000 “C for 15 s increases the luminescence intensity, mainly due to an increase in minority-carrier lifetime, which enhances the excitation efficiency. Luminescent Er forms clusters with oxygen: the maximum Er concentration that can be optically activated is determined by the 0 content, and is (3 2 1 j X 1017 E&m3 in Cz-Si. The internal quantum efficiency for electrical excitation of Er in Cz-Si is larger than 3X 10e6.