Trends in diffusion-length measurements in the original and dielectrically isolated-tub π-silicon as a function of processing

An EBIC (electron-beam-induced current) analysis of diffusion length and, hence, lifetime as a function of processing history of dielectrically isolated (DI) tubs and the original π-silicon was performed with a two-dimensional computer simulation. The simulation accounts for a pear-shaped excitation volume for the surface recombination at two sidewalls and the top and bottom surfaces and for excess electron diffusion to a planar junction with a planar back contact. The different processing histories include those which have undergone minimal high-temperature heat treatment (prior to and after DI-tub formation), a phosphorus getter, and a denuded-zone treatment. It is found that the DI-tub formation process results in a slight improvement in the diffusion length, but that the denuded-zero treatment results in a significant (ten times the diffusion length in untreated material) improvement in both the original and DI-tub π-silicon