Photoelectronic properties of a-Si:H and a-Ge:H thin films in surface cell structures

Abstract

We have grown thin films of a-Si:H and a-Ge:H by reactive magnetron sputtering and have studied their photoelectronic properties in surface cell structures. The dark and photocurrents do not obey the expected scaling laws with respect to changes in the sample thickness. This is explained in terms of a model which assumes depletion regions at both surfaces of the thin-film structure. We have analyzed the properties of such structures and have used the thickness dependence of the dark current and activation energy to estimate: (1) the defect concentrations near the Fermi level and (2) the amount of surface band bending. Defect densities so obtained are in agreement with those determined from space-charge limited currents (SCLC’s) and photodeflection spectroscopy (PDS).

Spectroscopic and electrical detection of intermediate phases and chemical bonding self-organizations in (i) dielectric films for semiconductor devices, and (ii) chalcogenide alloys for optical memory devices

“…The first part of this sub-section address measurements that have identified important differences at the interfaces between a-Si:H and a-SiO 2 and a-SiN:H that clearly establish the superiority of a-SiN:H, and make that the preferred dielectric for a-Si TFT devices [14][15][16]. Dark-and photoconductivity (PC) studies of a-Si:H interfaces with a-SiO 2 dielectrics have been made using a surface cell geometry [14].…”

“…Dark-and photoconductivity (PC) studies of a-Si:H interfaces with a-SiO 2 dielectrics have been made using a surface cell geometry [14]. By studying dark-conductivity as a function of the a-Si:H thickness an up-ward surface band-bending of $0.2 eV was found at the a-Si:H/a-SiO 2 interface.…”

Reduction of bonding constraints by self-organization in gate dielectrics for a-Si:H thin film transistors (TFTs) and crystalline Si field effect transistors (FETs)

“…Dark-and photo-conductivity studies of a-Si:H interfaces were made using a surface cell geometry [1]. By studying these conductivities as functions of a-Si:H film thickness and the wavelength of the visible light, an upward surface band-bending of $0.2 eV was observed at the a-Si:H-SiO 2 interface.…”

“…Section 2 presents research results that describe the properties of thin films of non-crystalline SiO 2 and Si 3 N 4 :H deposited at low temperatures, 300°C directly onto a-Si:H substrates. Interface properties have been studied by analysis of photo-and dark-currents in sandwich and surface cell geometries [1,2], and these results have been correlated with threshold voltages in TFTs. The optimum dielectric aSiH is shown to a heavily hydrogenated Si-N-H alloy with approximately 28% Si, 42% N and 30% H. In marked contrast SiO 2 is the optimum gate dielectric for lc-Si:H [3].…”

Reduction of bulk and interface defects by network self-organizations in gate dielectrics for silicon thin film and field effect transistors (TFTs and FETs, respectively)

“…This processing temperature establishes the H-atom concentrations in nc-Si:H channels, and doped nc-Si source and drain contacts required for optimization of device performance and reliability. The dielectric/nc-Si interfaces have been studied by analysis of photo-and dark-currents in sandwich and surface cell geometries [1,2]. These results have been correlated with threshold voltages for electrical switching in TFTs.…”