The structure of Si:Er layers grown by molecular beam epitaxy onto Si(001) substrates was investigated by transmission electron microscopy. A study was made of the dependence of the layer structure on the Er concentration, [Er] (8 x 1018 - 4 x 1019/cm3) as well as the epitaxial growth temperature (400 to 700C). In general, ErSi2 platelets and spherical metallic precipitates were formed during the epitaxial growth through the layer and in the near-interface region, respectively. For [Er] greater than 2 x 1019/cm3, an oscillation of platelet density with periodicity of 200 to 250nm was observed. A new type of complex structural defect was observed in a specimen with [Er] = 4 x 1019/cm3. In the layers grown at 400C, complexes of extended defects consisting of partial dislocations, stacking faults and twins were generated. The formation of silicides and Er precipitates was accompanied by emission of vacancies, which leads to the formation of pores in the layer. A high concentration of vacancies should also result in formation of V-V and V-Er complexes. The presence of these point-defect complexes could explain the appearance of deep acceptor levels with an activation energy of 360meV, which could be responsible for non-radiative paths.

Crystal Lattice Defects in MBE Grown Si Layers Highly Doped with Er. N.D.Zakharov, P.Werner, V.I.Vdovin, D.V.Denisov, R.N.Kyutt, N.A.Sobolev: Physica Status Solidi A, 2008, 205[2], 282-8