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.
A Method for the Measurement of Short Minority Carrier Diffusion Lengths in Semiconductors
A method is presented whereby short minority carrier diffusion lengths in semiconductors may be determined by measuring the variation of surface photovoltage as a function of optical absorption coefficient. The method does not depend upon the specific form of the relationship between the surface photovoltage and the density of the excess minority carriers injected at the bulk edge of the surface space charge region. Only capacitive contacts to the sample are needed for the measurement. The method has been used to determine the minority carrier diffusion length in both n and p type gallium arsenide.
Effect of a new inhibitor of cholesterol biosynthesis (AY 9944) on serum and tissue sterols in the rat.
AY 9944 is a novel inhibitor of cholesterol biosynthesis which appears to act on the Delta 7-reductase enzyme, interfering with the conversion of 7-dehydrocholesterol to cholesterol. In all tissues studied, with the exception of the lens, there was a reduction in cholesterol and a marked accumulation of 7-dehydrocholesterol. Isotope studies showed a reduced uptake of acetate into cholesterol, and an increased uptake into 7-dehydrocholesterol, in various tissues in vivo and by skin samples in vitro. There was no apparent accumulation of lanosterol or of the methostenols in the rat skin.