Modellierung, Herstellung und Optimierung von a-Si:H Mehrfarbdioden für eine verbesserte Farbseparation

The object of this PhD thesis is the development of novel light sensitive and spectral selective photodiodes based on amorphous silicon and its alloys. Typically, color selectivity of state of the art crystalline silicon sensors is achieved by stacking additional optical filter arrays on sensors surfaces being just sensitive to light intensity. The wavelength dependent optical absorption in amorphous silicon combined with an adequate $mutau$-engineering of the absorbing multilayer stack, results in a field-adjustable drift-profile. This enables the opportunity to manipulate the spectral response. The sensor architectures developed are capable to generate almost an infinite number of space-resolved color information signals in just one single sensing device. The development process presented ranges from simple light intensity detectors to multicolor sensors with an optimized discrete bandgap structure. At the end of the process, characteristics of high complex and continuous bandgap adjusted hyperspectral sensors are discussed. Detector development requires an exact and well-founded knowledge of electro-/optical characteristics of the thin film layers; these are absorbing-, doping- and contact thin films. In this work, a variety of layers is examined by current-/voltage-, spectral sensitivity- and constant photocurrent measurements. Beneath optical simulations to analyze absorption-, reflection- and transmission spectra, scanning electron microscopy studies were performed to monitor film thicknesses, etching processes and the structural quality of the deposited thin films. An additional focus is put on the transient and capacitive behavior of the devices developed. To understand physical fundamentals like transport-, generation- and recombination processes in an amorphous hydrogenated silicon pin-photosensor, a simple analytical model and a more complex numerical model of a-Si:H devices are compared to calculate essential parameters like current density. Furthermore, those models support the interpretation of the measurement results. Especially, the course of the electrical field and the product of charge carrier mobility and life-time, the mutau-product, give an insight in understanding the functionality of the devices presented. This special transport parameter defines the drift-length, the fundamental value enabling a voltage adjustable spectral response. Those models do not allow a fully characterization of the spectral response curves, but they support the fundamental understanding of the devices functionality and help in interpreting the measurement results. In this work, a model describing the correlation between the cathode material and the interference fringes, occurring in the falling edge of the spectral response, is developed and highlighted in a separate chapter. One of the main research results being presented in this work is the realization of an innovative hyperspectral sensor being not just sensitive in the visible spectral range, but being able to scan optical signals in the near ultraviolet, too. Another highlight presented, is the development of a novel process, enabling an in-situ structuring of thin films in a high vacuum process, without etching the material with a fluid solvent. At the end of this thesis, an innovative sensor structure comprising an internal, discrete a-Si:H filter structure which successfully suppresses the green sensitivity of a multicolor sensor is characterized. All thin film detectors presented, reveal that this kind of innovative sensor technology is predestined to be used in color recognition systems. Therefore, they offer a lot of potential for improvement and redevelopment. Possible sensor applications may exist in fields of civil security technologies, for example in the detection of hazardous materials, like explosives or illegal drugs. Moreover, applications in fields of environmental engineering are imaginable to classify waste or tissue samples. These sensors also may be useful for improving photovoltaic cells, medical diagnostic tools, fluorescence and spectrophotometric measurement systems, chemical analysis tools or colorimetric and hyperspectral imagery systems.