Steven J. Grammatica

Geminate and non-geminate recombination in a-As2Se3

Combined zerographic measurements and a delayed-collection field technique has been applied to a-As2Se3. The data shows that the zero-field quantum efficiency is 0.45±0.02. The measured field and temperature dependence gives a best fit to the Onsager theory with r0=80 A for Φ0=1. Non-geminate recombination was studied using a delayed-collection field technique as a function of the time delay of the collection field. The results indicate a remarkably long recombination lifetime≈1 sec at room temperature which is diffusion-controlled.

Field‐effect phenomena in hydrogenated amorphous silicon photoreceptors

The imaging properties of hydrogenated amorphous silicon (a‐Si:H) photoreceptors overcoated with insulating passivation layers are discussed. Field‐effect phenomena are shown to interfere with the electrophotographic imaging process in this device configuration. Since photoreceptors are majority carrier devices and a‐Si:H is an extrinsic material, the field‐effect phenomena can be counteracted by proper doping of the a‐Si:H‐insulator interface.

Geminate recombination‐controlled photogeneration in amorphous solids

Experimental and theoretical results are presented which suggest a unified picture of photogeneration processes in amorphous selenium and hydrogenated amorphous silicon. The different wavelength dependent quantum efficiency of photogeneration in these technologically important materials can be explained by a geminate recombination model if account is taken of their different dielectric constants.

Photoelectronic properties of hydrogenated amorphous silicon/silicon oxide heterostructures

A glow‐discharge hydrogenated amorphous silicon/insulator heterostructure has been characterized by a range of measurements including optical absorption, temperature dependence of photo‐ and dark conductivity, internal photoemission, xerographic discharge, and spectral dependence of photoconductivity. Efficient injection of dark and photocarriers from amorphous hydrogenated silicon into, and transport through, relatively thick SiOx:N:H has been achieved. Unlike the conventional thermal oxide on Si, no significant energy barrier to injection is found in the plasma‐deposited heterostructure. The use of the structure as a potential xerographic device is demonstrated. A mobility lifetime product as high as 6×10−10 cm2/V and a transport process with an activation energy of ∼0.3 eV is found for electrons in the SiOx:N:H films.

On the field-effect in amorphous tetrahedral photoreceptors

Abstract The imaging properties of photoreceptor structures based on amorphous silicon are discussed. When the external surface of such structure is an electrically insulating film, it functions during the imaging process like the gate insulator in a thin film transistor. The resulting field effect phenomena are shown to decrease the attainable electrophotographic resolution. Methods are discussed to counteract the occurence of the field effect in photoreceptors made of tetrahedrally bonded amorphous materials.

Xerographic measurements in compensated hydrogenated amorphous silicon

Xerographic discharge measurements are reported on 10‐μm‐thick compensated hydrogenated amorphous silicon samples for doping levels as high as 5000 ppm by weight. Excellent xerographic characteristics including photosensitivity, charge acceptance, and hole range are maintained up to doping levels ∼ 100 ppm by weight. Beyond this both charge acceptance and hole range degrade due to associated increases in mid‐gap‐state densities.

Hole range in compensated hydrogenated amorphous silicon

Abstract Xerographic discharge measurements are reported on 10 μm thick compensated hydrogenated amorphous silicon samples for doping levels as high as 5000 ppm by weight. Excellent xerographic characteristics including photosensitivity, charge acceptance and hole range are maintained up to doping levels ∼100 ppm by weight. For higher doping levels both charge acceptance and hole range degrade due to associated increases in mid gap state densities.

Piiotoelectronic Proiioerties Of Amorpiious Silicon/Silicon Oxide Heterostructures

A glow-discharge deposited a-Si:H/insulator heterostructu re has been characterized by a range of measurements including optical absorption, internal photoemission, xerographic discharge and spectral dependence of photoconductivity. Efficient injection of photocarriers from a-Si:H into, and transport through, films of SiOx:N:H up to 10 μm thick has been achieved. Unlike the conventional thermal oxide on Si, no significant energy barrier to injection is fotInd in the plasma deposited heterostructure. The use of the structure as a potential xerographic device is demonstrated. A mobility lifetime product as high as 6 x 10 -10 cm 2 /volt is found for electronsin the SiO x :N:H.