CARRIER LIFETIME MEASUREMENTS BY MICROWAVE PHOTOCONDUCTIVE DECAY METHOD AT LOW INJECTION LEVELS

The minority carrier lifetime of Si wafers has been measured at very low injection levels by employing a newly developed microwave photoconductive decay (mu-PCD) technique. It is found that the effective lifetime is dramatically increased for the case of p-type Si when the injection level is reduced to two orders of magnitude less than the equilibrium value. In contrast to this, the n-type wafer lifetime remains almost un-changed even upon lowering the injection level. Also, it is shown that the different contamination levels of Fe in Si wafers are clearly discriminated by the measured lifetime.