Increase in effective carrier lifetime of silicon at low carrier injection levels

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Abstract
The increase in the effective carrier lifetime of oxidized p-type silicon at low carrier injection levels is studied from the viewpoint of silicon surface effects. The effective carrier lifetime is measured by a microwave photoconductive decay method. A gold/oxide/silicon structure is used to examine the dependence of effective carrier lifetime on injected carrier concentration. The effective carrier lifetime is measured at various voltages applied between the gold electrode and the silicon substrate in order to change the silicon surface conditions, i.e. accumulation, depletion or inversion. Increase in the effective carrier lifetime at low carrier injection levels is observed only when the inversion layer is induced at the silicon surface. The increase in effective carrier lifetime may be due to slow recombination of excess minority carriers stored in the inversion layer at the SiO2/Si interface with a low interface trap density and/or slow diffusion of the excess minority carriers into the bulk of the silicon.