Using an original test structure we show by numerical simulations that the open circuit voltage decay (OCVD) method can be improved to obtain the spatial profile of the /spl tau//sub PO/, /spl tau//sub NO/ lifetime parameters along the epilayer of n-n+ wafers. The test structure consists of a surface diode including an additional n/sup +/ region, where the diode is used to inject minority carriers within the epilayer, the sense region allows one to measure the diode voltage without the series resistance effect, and finally a positive voltage applied to the n+ substrate is used to electrically control the epilayer volume where carriers recombine.