摘要
半导体发光二极管和半导体激光器是两种极为重要的发光器件，它们不但在电子仪表显示、照明、大规模集成电路、光存储、光通信等方面有着广泛的应用，在研究领域也一直以来倍受人们的关注。本文对半导体发光二极管的负电容和激光二极管的高速调制进行了较为深入细致的研究，其中的主要工作和取得的一些成果可以概括如下：
（1）、通过实验证明采用我们发展的正向交流小信号法来检测二极管的正向交流电特性是一种准确的方法，由此得到的正向电容谱的灵敏度极高，可以在分析器件结构和内在物理机制等方面提供很大帮助，是对现有的高度成熟的反向电容谱技术一个很好的补充。
（2）、采用基于并联和串联模式的交流小信号法对半导体发光二极管的正向交流电特性进行了检测，测试结果表明半导体发光二极管中普遍存在着负电容。进一步的发光特性实验表明，半导体发光二极管中的负电容与强复合发光过程有着紧密的关联。
（3）、依据正向交流小信号实验和发光特性实验，我们对发光二极管的负电容进行了物理机制上的定性解释，并首次尝试了从微观输运机制上去定量解释。
（4）、详细研究了半导体激光器的本征和寄生频率调制响应特性，并对影响半导体激光器的本征和寄生频率调制响应的主要因素作了系统的探讨。
（5）、首次提出了一个全新的利用负电容来补偿半导体激光器芯片寄生电容的设想，并对此设想在技术上的可行性进行了探讨。
（6）、提出了一个新的研究方向，即当整个器件的总电容为负值的时候，半导体激光器在交流小信号测试下的频率调制响应特性会出现什么样的现象。这是一个目前不为人们所知的在研究方面的空白。
总之，由于半导体发光二极管的负电容可能会对器件的频率特性、开关特性以及其它一些特性产生影响，因此，在定量的层次上去正确认识发光二极管的负
电容，不论在理论上还是在实际应用中都具有重要的意义。此外，我们提出的利用负电容补偿半导体激光器件寄生电容的设想一旦在技术上被证明可行的话，那其价值将是颇为可观的，因为它不但能使人们在如何减小寄生电容这一问题上的研究思路大为拓宽，甚至有可能对整个高速半导体激光器产业的发展产生积极的影响。
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.
引文
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