![]() ![]() Further technological progress included: solar cells 27, 28, integrated circuits 29, 30, light-emitting diodes 31, solid-state laser sources 32, charge-coupled devices 33 etc. Even though the theoretical basis provided by Alan Wilson represented a significant leap forward in the semiconductors science and technology, it was the emergence of both silicon (Si) and germanium (Ge), as semiconductor materials, that effectively prompted the extraordinary achievements in the field − initially, with the development of p-n junctions 17, 18, 19, 20, 21, 22, 23 and, later on, with the realization of semiconductor triodes or, the transistors 24, 25, 26. In fact, the skepticism involving these materials was so intense that the word semiconductor ( halbleiter in German) − suggesting its real electrical characteristics − was introduced only in 1911 by Josef Weiss, at that time, a student of Professor Johann Koenigsberger 15, 16. Such a long journey took place because of the suitability of the vacuum electron tubes in electronic applications 13, 14 but, mainly, because of the absence of good-quality ( i.e., impurity-controlled) semiconductor materials − rendering erratic or non-reproducible series of experimental results. Since the very first studies by Alessandro Volta of the so-called cattivi conduttori in the 18th century 3 passing by all the experimental work of Humphry Davy 4, Michael Faraday 5 and Wilhelm Hittorff 6 and the discovery of the photovoltaic 7, 8 and rectification effects 9, 10 it was a long way until some of the properties of the semiconductors have been (partially) elucidated by the quantum theory of electrons developed by Alan Wilson in 1931 11, 12. In view of these characteristics, a new−unified methodology based on the fitting of the absorption spectrum with a Boltzmann function is being proposed to efficiently determine the optical bandgap of semiconductor materials.įor a long time, the distinctive electrical behavior exhibited by semiconductor materials has fascinated the humankind 1, 2. Additionally, it complies with the requirements of direct, indirect, and amorphous bandgap semiconductors, and it is able to probe the (dis)order of the material as well. The method is straightforward and, contrary to the traditional approaches to determine E gap, it is exempt from errors due to experimental spectra acquisition and data processing. The detailed analysis of the experimental results indicates that accurate E gap values can be obtained by fitting a sigmoid (Boltzmann) function to their corresponding optical absorption spectra. Stimulated by these aspects, this work investigated the semiconductors silicon, germanium, and gallium-arsenide in the crystalline (bulk and powder) and amorphous (film) forms. Within this context, optically-based methods were of special importance since, amongst others, they presented details about the electronic states and energy bandgap E gap of semiconductors which, ultimately, decided about their application in devices. Such a progress comprised the development of materials and models that, allied to the knowledge provided by spectroscopic techniques, resulted in the (nowadays) omnipresent electronic gadgets. Along the last two centuries, the story of semiconductor materials ranged from a mix of disbelief and frustration to one of the most successful technological achievements ever seen. ![]()
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