Showing papers by "Chenming Hu published in 1978"

Determination of diffusion length and surface recombination velocity by light excitation

Abstract: The current induced by a monochromatic light source in a Schottky barrier or p−n junction perpendicular to the sample surface is analyzed. Expressions for the induced current are derived for a scanning light spot and for uniform illumination with part of the sample shadowed. A uniform illumination induces a current that is more nearly an exponential function of the distance between the junction and the illuminated area than a moving spot. When the effect of surface recombination is strong, an alternative method of deducing the diffusion length from the measured current is suggested. The surface recombination velocity may be determined from the dependence of the collected current on the optical penetration depth in a simple manner.

Determination of nonuniform diffusion length and electric field in semiconductors

Abstract: A method is proposed that purports to measure the non-uniform diffusion length L(x) in the presence of an arbitrary electric field E_{x}(x) . A point source of carrier generation (as a model for an electron beam) scans across the sample in the thickness direction x while the induced currents are measured at two reverse-biased junctions sandwiching the sample. L(x) and (E_{x} \micro_{p} + D_{p})/D_{p} can be deduced from the currents. If only one collecting junction is present, one of the two functions may be deduced provided that the other is known; in addition, the surface recombination velocity at the other boundary may be determined in the presence of arbitrary L(x) and E_{x}(x) . With additional scanning in the y and z directions, quasi three-dimensional mapping is possible.