| Summary: | 碩士 === 國立臺灣大學 === 物理學研究所 === 89 === Abstract
Optical properties have been investigated in InAs(N)/InGaAs single quantum wells (SQWs) on InP grown by gas source molecular beam epitaxy.Measurements of temperature dependent photoluminescence, excitation power dependent photoluminescence, and photoconductivity have been employed in our study. In order to improve the material quality, the methods of rapid thermal annealing (RTA) under nitrogen environment and hydrogen passivation have been performed. Interesting results have been obtained and will be reported in this thesis.
As the nitrogen concentration increases, the peak energy of PL spectra decreases. It indicates the existence of a bowing effect in InAsN alloy. Through a detailed study of the dependence of PL spectra on temperature, pumping intensity and nitrogen content, we point out that the occurrence of PL in InAs(N)/InGaAs quantum wells arises from the localized states due to potential fluctuations induced by the incorporation of nitrogen in InAs. We use nitrogen annealing and hydrogenation as two different methods to improve the InAsN single quantum wells (SQWs). After rapid thermal annealing with the optimum temperature, both the PL intensity and linewidth can be significantly improved, and we show that the incorporation of atomic hydrogen into InAsN/InGaAS quantum wells can effectively passivate defects. Thus, it leads to the enhancement of exciton luminescence intensity. After hydrogenation, the change of the optical properties is quite different from that of the annealing with nitrogen treatment. For instance, the linewidth becomes wider after hydrogenation, while the linewidth is narrower after nitrogen annealing. Through a detailed study of the photoluminescence spectra, we point out that the passivation of defect bonds is the main reason for the improved optical behavior for hydrogenation, while the As-N interdiffusion is responsible for the change after nitrogen annealing.
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