Deep Level Generation-Annihilation in Nitrogen Doped FZ Crystals

Abstract

ABSTRACTNitrogen atoms exist in silicon as non-reactive nitrogen molecules. This is concluded from two I-R absorption experiments: one is the nitrogen isotope effects on N- N pairs and the other is silicon isotope shifts at 10 K. Intrinsic resistivities (over 20 K ohm-cm) are obtained by annealing at 1000°C, 1 min. in N2 in both p- and n-type nitrogen doped thin wafers. Resistivity increases are due to deep- level generations: 0.66 eV above the valence band for p-type and mainly 0.44 eV below the conduction band for n-type material. These deep levels are considered to be formed by nitrogen pairs and divacancies which are incorporated during growth. Since divacancies are easy to out diffuse to the wafers surface, the deep levels are also irreversibly removed. Diffusion coefficient of Si intersititialswici'ch are annihilated with divacancies in the lattice are calculated as 6×10−6cm2/s and 2×10−6cm2/s at 900°C and 1000°C respectively. Migration energy of Si interstitials is about 4.5 eV.