Decay of the electronbeaminduced current in hydrogenated amorphous silicon devices

The electron beam induced current technique was used to study electron energy loss in amorphous hydrogenated silicon a-Si:H. This study leads to the determination of the electron generation function which is needed when using the variable energy electron beam induced current technique (EBIC) analysis of a-Si:H device. A series of identical n-i-p a-Si:H diodes with a thin aluminium top electrodes were fabricated and varying thicknesses of a-Si:H layer were deposited on it. In EBIC measurements, the n-i-p diode was reverse biased at maximum potential. The electron range of a-Si:H was determined directly by measuring the energy at which the electron beam is completely stopped in the top layer and no carrier generation is possible in the n-i-p diode. The generation function is then deduced from EBIC contrast measurements between the aluminium electrode and the top a-Si:H layer.

Stoichiometric amorphous GaAs films with intrinsic properties have beer produced by R.F. Sputtering in pure argon at high substrate temperature of 290°C. The electronic and the optical properties of this material have been modified by the molybdenium co-sputtering. This paper reports: on several modified material parameters including the electrical conductivity, thermal activation energy and optical gap. Atomic Mo concentrations up to 1.24% have been investigated. It is observed that the room temperature conductivity can be controlled over about six orders of magnitude, which corresponds to a shift in the Fermi level of 0.45 eV towards the conduction band edge. For optical parameters, the optical gap has been reduced by 0.1 eV. An additional absorption tail due to localized states introduced by doping atoms is observed. It is concluded that our a-GaAs have the main requirement, i. e low density of defect gap states, for effective doping with analogy to a-Si prepared either by glow discharge or by sputtering in argon-hydrogen plasma.

The characterization of a-Si:H structure, using an electron beam in the keV range, is an interesting alternative to the more common photon beam techniques. a-Si:H device characterization by the determination of collection efficiency and other electronic parameters can be performed by variable energy EBIC method. But this requires an accurate knowledge of electron generation function and electron range in a-Si:H. In this paper we present an experimental determination of electron generation function and electron range in a-Si:H. To do this, a series of identical n-i-p a-Si:H diodes with a thin aluminium top electrodes were fabricated and varying thicknesses of a-Si:H layer were deposited on it. In EBIC measurements, the n-i-p diode was reverse biased at maximum potential. The electron range of a-Si:H was determined directly by measuring the energy at which electron beam is completely stopped in the top layer and no carrier generation is possible in the n-i-p diode. The generation function is then deduced from EBIC contrast measurements between the aluminium electrode and the top a-Si:H layer.