Analysis of n(+)p silicon junctions with varying substrate doping concentrations made under ultraclean processing technology

Using highly controlled ultraclean processing technology, marked improvements in n(+)p Si junction quality are achieved presenting a theoretical significance. Boron-doped substrates with various boron doping concentrations N-s were As+ implanted, forming the n(+) junction sides. The diffusion (Id) and generation (I-gen) currents, as well as the ideality and the generation factors, are significantly reduced, and bulk generation lifetimes are prolonged. Using Shockley-Read-Hall theory it is found that a deviation of the trapping centers energy (E(t)) from the midband-gap energy (E,) is responsible for the improvements. The experimental results show that \E(t)-E(i)\ is a function of N,, and that the I-gen/I-d ratio is significantly low. Accordingly, it is proposed that I-gen/I-d ratio should be regarded, under certain conditions, as a figure of merit for junction quality. It is concluded that the \E(t)-E(i)\ deviation is related to the ultraclean processing technology used, due to the formation of new energy levels far from Ei and the suppression of introduction of new energy levels near Ei. Surface generation currents were found experimentally to be significant, and thus not negligible. Surface effects in general demonstrated similar trends to the bulk generation effects. (C) 1997 American Institute of Physics.