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Negative Capacitance And High-Speed Modulation Of Semiconductor Light-Emitting Devices

Posted on:2004-07-14Degree:MasterType:Thesis
Country:ChinaCandidate:Z B CengFull Text:PDF
GTID:2168360125462865Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Semiconductor light-emitting diodes (LEDs) and laser diodes (LDs) are two very important light-emitting devices due to their wide application in many fields, such as display, lighting, integrate circuit, light-storage, light-communication, etc. It is so important for LEDs and LDs that the studies related to their electrical and optical characterization have been a very intresting subject in the past and today. In this paper, negative capacitance of LEDs and high-speed modulation of LDs are studied at the same time, and our work and achievement can be summarized as follows:(1). The experiments verified that the forward ac small signal method developed by us could be an accurate method to measure the ac electrical characteristics of semiconductor diodes. The forward capacitance-voltage spectrum with a very high sensitivity, obtained by the forward ac small signal measurement method, could offer much help to analyze the microscopic transport mechanism of a semiconductor diode, and thus is a good complementarity to the current highly-mature reverse capacitance-voltage spectrum.(2). We tested the electrical characteristics of LEDs using the forward ac small signal method based the series and parallel modes, and the experimental results show that there are negative capacitance in most semiconductor LEDs. The further electroluminescence experimental result shows that negative capacitance of LEDs is related to the radiative recombination of the injected carries.(3). On the basis of the experiment of both forward ac small signal and electroluminescence, we made a qualitative explanation to the negative capacitance of LEDs from physics mechanism, and we also try to make a quantitative explanation to the negative capacitance of LEDs from microscopic transport mechanism and have acquired some progress at the quantitative explanation.(4). We made a detail study to the characteristics of the intrinsic and parasitic frequency modulation response of LDs, and finished a systemic discussion to the main factors affecting the characteristics of the intrinsic and parasitic frequency modulation response.(5). For the first time we put forward a novel idea to compensate the parasitic capacitance of LDs by using a negative capacitance. Besides, we also discuss the idea's feasibility in practice.(6). A new study subject was put forward, which is that what the frequency response of LDs would be when the whole capacitance of LDs is negative. The new subject is worth to investigate because it possibly hides much important information.In a word, the quantitative explanation to the negative capacitance of LEDs has a very important significance both in theoretical field and in practical application, for negative capacitance of LEDs could possibly cause some effect on modulation, pulse and switch circuits. Besides, if it is to prove feasible in practice, the novel idea to compensate the parasitic capacitance of LDs by using a negative capacitance is rather valuable, for it not only could widen people's study thought about how to minish the parasitic capacitance of LDs, but also could probably cause a positive influence on the development of the whole industry of high-speed semiconductor lasers.
Keywords/Search Tags:Light-emitting diode, Forward ac small signal method, Negative capacitance, Laser diode, Modulation bandwidth, Frequency response, Parasitic capacitance
PDF Full Text Request
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