Improvements in method and apparatus for determining minority carrier diffusion length
The constant-magnitude steady-state surface photovoltage (SPV) method for determining the minority carrier diffusion length L is in principle an excellent technique. It has, however, recevied relatively limited use because of practical difficulties in carrying out the required measurements. This paper describes an improved measurement system that virtually eliminates these difficulties and allows a rapid straightforward determination of L. These measurements in silicon monitor wafers have enabled a routine quality control check on many factory processing steps, particularly those that are carried out at high temperature and have the potential for significantly degrading L.
Silicon-wafer-surface damage revealed by surface photovoltage measurements
Anomalous results of surface photovoltage (SPV) measurements on Si wafers are shown to be associated with a damaged region beneath the illuminated surface of the wafer being measured. The anomaly is a concave‐upward curvature of the I0(α−1) plot with an r2 value, derived from linear regression analysis, less than the normally observed minimum value (∼0.98). Removal of the damaged region by an appropriate etching procedure allows subsequent SPV measurements whose results are substantially free of the previously observed anomaly. The qualitative character of the anomaly can be reproduced by a simple theoretical model in which only one effect of the damage is considered; this effect is a diminished quantum efficiency for hole‐electron pair generation by photon absorption in the damaged region. The results suggest the use of SPV measurements as a test procedure for revealing the presence of surface damage in Si wafers.
XIII. Photovoltaic and Photoconductive Theory Applied to InSb
Equations are formulated for the distribution of photo-electrons and photo-holes in an intrinsic material. From the results for the photovoltaic effect it is shown that a value for the ambipolar di...