In this work, the theory of internal photoemission is reviewed and extended for the special case of platinum silicide Schottky barrier infrared photodiodes. Vickers' model of hot-electron-mode photodetection is recast in terms of hot-holes, and the effects of carrier energy loss due to phonon collisions, as well as the depletion of the occupation of the emitting states due to emission are included. The optical absorption of the Schottky diodes is measured and used to relate the quantum efficiency of the diodes to the internal yield as calculated from the model. By including the effects of the carrier energy loss due to phonon collisions and the depletion of the occupation of the emitting states in the model, one can resolve previously unexplained anomalies in the photoresponse data (the shape of the Fowler plots, the absolute magnitude of the yield, and the difference between the optical and thermal barriers). Independent estimates are obtained for the mean-free-path between hot-hole/phonon, hot-hole/cold-electron, and hot-hole/imperfection collisions as well as the mean phonon energy, mean transmission coefficient across the Schottky barrier, and the Fermi energy. The model is found to be in excellent agreement with the experimental data for parameter values consistent with those reported in the literature. Some degree of correlation is found to exist between the one free variable for each diode and the processing used for that diode. Namely, the temperature of the substrate during deposition is correlated with the value of the mean-free-path between imperfection scattering events.

Thesis (M.S. in Electrical Engineering)--Vanderbilt University, 2003. / Title from PDF title screen. Includes bibliographical references.

No description available.

Thesis (M.S. )--Youngstown State University, 2007. / Includes bibliographical references (leaves 68-69).

No description available.

This thesis investigates the use of an avalanche Platinum Silicide (PtSi) Schottky Barrier Diode as a detector in fiber optic communication systems for the 1.3 to 1.5 mum spectral region. The avalanche process is used to amplify the signal prior to electrical interfacing in order to enhance the signal-to-noise ratio. The amount of multiplication is predicted by the impact ionization coefficients for electrons and holes, alpha and beta, respectively. By using PtSi Schottky diodes, where alpha > beta, pure electron injection can be accomplished by irradiating with photons of energy psi hnu Eg (where psi is the Schottky Barrier height and Eg is the bandgap of silicon), thus maximizing multiplication and minimizing noise. An alternative means for avalanching involves the quantum effects of impurity-band ionization. By using a heavily doped semiconductor and operating at low temperatures, one can achieve noise-free gain at lower electric field strengths. (Abstract shortened with permission of author.)

An experimental and theoretical analysis of the effects of ion bombardment on Schottky diodes is presented. The experimentally observed shifts in diode performance are compared to the conditions of ion exposure. These experiments show that Schottky diodes exposed to ion beams show decreases in effective barrier heights and ideality factors, as well as increased incidence of premature reverse breakdown. The change in barrier height is found to be proportional to the energy of the individual ions and the total number of ions delivered to the surface. A numerical simulation of the damage process and device performance is developed. The model considers only the effect of ion exposure on the potential distribution within the metal-semiconductor junction. Comparison of experimental and modelled barrier shifts shows fair agreement, suggesting that enhancement of tunnelling currents is the dominant mechanism for barrier lowering.

Recent advances in growth techniques have lead to the production of high quality GaN and this has played a vital role in the improvement of GaN based devices. A number of device types can be produced from GaN. Spectrally selective devices can be produced by creating ternary or quaternary material systems by partially substituting either Al or In for Ga in GaN. This allows a wide spectral range that can be achieved ranging from the visible to the ultraviolet. The applications of detectors based on these material systems are vast and include areas such as biological, military, environmental, industrial and scientific spheres. In front illuminated Schottky barrier photodetectors, two major factors influencing the sensitivity of the device are the reverse leakage current and the transparency of the Schottky contact. In order to reduce the reverse current of semiconductor based devices, increase the barrier height, and enhance the adhesion of a metal on a semiconductor it is important to subject the contact to annealing. Annealing studies have been performed on AlGaN based photodiodes to investigate the evolution of the optical and electrical properties. In this study, the electrical and optical characteristics of AlGaN based Ni/Au and Ni/Ir/Au Schottky photodiodes were investigated. The electrical properties of the photodiodes were optimised by annealing in an Ar ambient. An increase in the Schottky barrier height and a decrease in the reverse leakage current were observed with increasing annealing temperature up to 500 oC. This effect was observed for both the Ni/Au and Ni/Ir/Au photodiodes. The optical characteristics of the photodiodes, which include the responsivity and the quantum efficiency, were also investigated. UV/visible rejection ratios of as high as 103 were obtained. The transmittance of Ni/Au and Ni/Ir/Au metal layers deposited on a quartz substrate were optimised by annealing. This was under the same ambient conditions as the Schottky photodiode. The transmittance increased with annealing temperature for the Ni/Au metal layer whereas it decreased at higher temperatures for the Ni/Ir/Au layer. The transmittance of the Ni/Au metal layer reached as high as 85 % after 500 oC annealing. The transmittance of the Ni/Ir/Au only reached a high of 41 % after 400 oC annealing. / Dissertation (MSc)--University of Pretoria, 2013. / Physics / unrestricted

published_or_final_version / abstract / toc / Physics / Master / Master of Philosophy

Wide bandgap semiconductor photodiodes were investigated for their suitability as radiation detectors for high temperature applications (≥ 20 °C), through measurements, calculations of key parameters of the devices, and relating the results back to the material, geometry of the detectors, environment under which the detectors were investigated, and previously published work. Three families of photodiodes were examined. 4H-SiC vertical Schottky UV photodiodes with Ni2Si interdigitated contacts were characterised for their response under dark and UV illumination. Electrical characterisation up to 120 °C and room temperature responsivity measurements (210 nm to 380 nm) suggested that the devices could operate at low UV light intensities, even at high visible and IR backgrounds without the use of filters, and at high temperatures. 4H-SiC Schottky photodiode detector arrays with planar thin NiSi contacts were investigated for X-ray (≤ 35 keV) detection and photon counting spectroscopy at 33 °C. The electrical characterisation of the devices up to 140 °C and subsequent analysis suggested that the devices are likely to operate as high temperature X-ray spectrometers. Results characterising GaAs p+-i-n+ mesa photodiode detectors for their room temperature visible and near infrared responsivity (580 nm to 870 nm), as well as their high temperature (≤ 60 °C) X-ray detection performance (at 5.9 keV) are presented. GaAs p+-i-n+ mesa photodiodes were also shown to be suitable for β- particle (electron) spectroscopy and X-ray fluorescence spectroscopy (≤ 21 keV) at 33 °C. The X-ray and electron spectroscopic measurements were supported by a comprehensive treatment of the noise components in charge sensitive preamplifiers. Calculations showed the potential benefits of using a SiC, rather than Si, JFET as the input transistor of such a preamplifier operating at high temperatures. The spectroscopic measurements, using both the 4H-SiC and GaAs photodiodes, are presented along with noise analysis to detangle the different noise components present in the reported spectrometers, identify the dominant source of noise, and suggest potential improvements for future spectrometers using the reported devices.