Masato Yamanobe

An experimental observation of photo-induced carrier multiplication in hydrogenated amorphous silicon

A photo-induced carrier multiplication in a hydrogenated amorphous silicon has been observed. A careful measurement of photo-carrier generation has been done with amorphous silicon Schottky barrier structure junctions as a function of incident photon energy in the range between 1.55eV and 6.2eV. The quantum efficiency is estimated to be multiplied by a factor of two in higher photon energy region than 5.4eV. This multiplication can be explained by an interband carrier ionization due to the energy given by a high energy photo-carrier.

Emission Microscope Observation of Metal–Insulator–Metal Emitters

Metal-insulator-metal emitters with an aluminum oxide insulating layer were investigated by making use of emission microscopy to observe the distribution and the fluctuation of electron emission. The microscope image showed a spotty pattern, indicating that the electrons were emitted from many separate sites on the surface. The density of spots reached 107 cm-2 under the driving voltage of 8.5 V. It was found that two types of emission sites having different power spectra of the fluctuation were randomly distributed on the surface. The different power spectra could be attributed to the formed and nonformed states of the emission sites.