Characterization of Cu and Ni Precipitates in n- and p-type Czochralski-grown Silicon by Photoluminescence

Photoluminescence (PL) images and micro-PL maps were taken on n- and p-type, Cu- and Ni-doped monocrystalline silicon wafers, in which the Ni and Cu had precipitated during ingot growth. Markedly different distributions of the precipitates were observed in the n- and p-type samples: in the n-type Cu-doped samples, a particle-lean ring structure was observed, dividing the sample into a central region and an edge region. Particles were distributed randomly in both regions, and those in the edge region had lower contrast, smaller sizes and higher densities than those in the central region. In the p-type Cu-doped samples, by contrast, the precipitates occurred in lines along <110> orientations. The Ni-doped samples showed similar features to the Cu samples. The different precipitation behaviours in n- and p-type samples are conjectured to be related to different concentrations of interstitials and vacancies in n- and p-type silicon.