An analytical method to separate the diffusion and generation components of pn junction leakage currents is developed. The voltage dependence between reverse current and capacitance in pn junctions is measured, and an approximately linear relationship between current density (J) and depletion width (W) is derived. In this relationship, the diffusion component corresponds to linearly extrapolated value of J at W=0, and the generation component corresponds to the rate at which J increases with W as voltage is applied. This method allows both components of the leakage current to be obtained for Czochralski, epitaxial, and intrinsic gettering wafers. Separated diffusion components strongly depend on silicon wafers mainly due to the change of minority carrier density and the diffusion of minority carriers. On the other hand, the generation component increases with increases in the electric field applied to the junction for all wafers. We found that this electric field effect on the generation component can be explained by the Poole–Frenkel mechanism.

We study the covariant entropy bound in the context of gravitational collapse. First, we discuss critically the heuristic arguments advanced by Bousso. Then we solve the problem through an exact model: a Tolman-Bondi dust shell collapsing into a Schwarzschild black hole. After the collapse, a new black hole with a larger mass is formed. The horizon, L, of the old black hole then terminates at the singularity. We show that the entropy crossing L does not exceed a quarter of the area of the old horizon. Therefore, the covariant entropy bound is satisfied in this process.

The reverse-bias leakage characteristics of silicon pn junctions have been investigated with particular attention to the effects of various types of oxygen-related defects, such as oxygen precipitates, oxidation induced stacking fault, and grown-in defects. The effects of oxygen-related defects on the leakage current of pn junctions in intrinsic gettering wafers and precipitation annealed wafers have been investigated quantitatively, and the field oxidation temperature used to form pn junctions has been found to be an important factor in determining the pn junction leakage current because oxygen-related defects are formed during low temperature field oxidation. It has also been found that grown-in oxidation induced stacking faults degrade the leakage characteristics. Grown-in defects that are well known to degrade the oxide breakdown characteristics were found to have some effects on the increase of the leakage current. In addition, it is recognized that the leakage current of pn junctions formed in wafers that have a relatively high concentration of interstitial oxygen has a transient component, caused by oxygen-related hole traps, which might also be the origin of the 1/f noise observed in pn junctions.

This letter reports the effect of organic matter on the growth of native oxide on a Si surface. Bare Si wafers and Si wafers with native oxide were stored under various conditions in a clean room and the thickness of native oxide was examined. In the case of the bare Si wafers, the native oxide hardly grew in a closed system but the native oxide grew to 6 Å in an open system when the storage time was 24 h. On the other hand, in the case of Si wafers with native oxide, this suggests that accumulation of organic matter occurs on Si wafers in the open system in the clean room. It was suggested that the accumulation of organic matter on Si wafers facilitates the growth of native oxide.