Electron paramagnetic resonance and photoluminescence study of Er-impurity complexes in Si

Abstract

Electron paramagnetic resonance ͑EPR͒ and photoluminescence ͑PL͒ spectroscopy have been used to examine the structure and optical properties of erbium-impurity complexes formed in float-zone Si by multipleenergy implants at 77 K of Er together with either O or F. After implantation a 2-m-thick amorphous layer was formed containing an almost uniform concentration of Er (10 19 /cm 3 )and O (3ϫ10 19 /cm 3 or 10 20 /cm 3 ) or F (10 20 /cm 3 ). Samples were annealed in nitrogen at 450°C for 30 min ͑treatment A͒, treatment Aϩ620°C for 3 h ͑treatment B͒, treatment Bϩ900°C for 30 s ͑treatment C͒ or treatment Bϩ900°C for 30 min ͑treatment D͒. Samples coimplanted to have 3ϫ10 19 O/cm 3 and subject to treatment C show a broad line anisotropic EPR spectrum. These samples have the most intense low-temperature PL spectrum containing several sharp peaks attributed to Er 3ϩ in sites with predominantly cubic T d symmetry. Increasing the O concentration to 10 20 /cm 3 produces sharp line EPR spectra the strongest of which are attributed to two Er 3ϩ centers having monoclinic C 1h and trigonal symmetry. The principal g values and tilt angle for the monoclinic centers are g 1 ϭ0.80, g 2 ϭ5.45, g 3 ϭ12.60, ϭ57.3°, g ʈ ϭ0.69, and g Ќ ϭ3.24 for the trigonal centers. The low-temperature PL spectrum from this sample showed additional sharp lines but the total intensity is reduced when compared to the sample with 3ϫ10 19 O/cm 3 . For the sample containing 10 20 O/cm 3 at least four distinct centers are observed by EPR after treatment B but after treatment D no EPR spectrum is observed. The PL spectra are also observed to change depending on the specific anneal treatment but even after treatment D, Er-related PL is still observed. Samples containing 10 20 F/cm 3 and annealed with either treatment B or C produced an EPR spectrum attributed to Er 3ϩ in a site of monoclinic C 1h symmetry with g 1 ϭ1.36, g 2 ϭ9.65, g 3 ϭ7.91, and ϭ79.1°.Tentative models for the structures of Er-impurity complexes are presented and the relationship between the EPR-active and PL-active centers is discussed. ͓S0163-1829͑99͒04503-8͔

Photonic Properties of Er-Doped Crystalline Silicon

“…In the case of line L 1 1 , the average g av value for the lowest level of the ground state is 6.1 AE 0.5, slightly smaller than the 6.8 value characteristic for pure À 6 and similar to values found for Er in different host materials [16], [67]- [70]. Therefore the lowest level of Er-1 ground state is likely to be of the À 6 character.…”

“…Extended X-ray absorption fine structure spectroscopy [13] revealed the presence of six oxygen atoms in the immediate surrounding of the local site of an Er atom in Czochralski (Cz) Cz-Si:Er [13], [14] and 12 Si atoms in float-zoned (Fz) Fz-Si:Er. These findings were confirmed by Rutherford back-scattering [15] and electron paramagnetic resonance studies [16]. Channeling experiments by Wahl et al [17] identified the formation of an Er-related cubic center at a tetrahedral interstitial site ðT i Þ as the main center generated in c-Si by Er implantation.…”

Structure of multi-oxygen-related defects in erbium-implanted silicon

“…[15] and based upon the similarities of the g values and point symmetry of centre OEr-3 to centre OEr-1, these two centres are believed to have very similar structures. However, the exact arrangement of these defect complexes within the Si lattice was unknown.…”

Er–O clustering and its influence on the lattice sites of Er in Si

“…It can be regarded as proven that O forms complexes with Er which directly modify the structural, electrical and optical properties of Er [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. However, there is also strong evidence that, possibly apart from ErO complex formation, additional mechanisms exist how O enhances the Er luminescence yield [6,7].…”