Date of Graduation

12-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Graduate School

Advisor

Gregory Salamo

Committee Member

Huaxiang Fu

Second Committee Member

Morgan Ware

Third Committee Member

Min Zou

Fourth Committee Member

Rick Wise

Keywords

InGaAs/GaAs, InGaN/GaN, Photoluminescence, Quantum Wells, Segregation, Simulation

Abstract

Recently, structures based on ultrathin quantum wells (QWs) began to play a critical role in modern devices, such as lasers, solar cells, infrared photodetectors, and light-emitting diodes. However, due to the lack of understanding of the formation mechanism of ultrathin QWs during the capping process, scientists and engineers cannot fully explore the potential of such structures. This study aims to investigate how structural parameters of ultrathin QWs affect their emission properties by conducting a systematic analysis of the optical properties of In(Ga)As/GaAs and In(Ga)N/GaN ultrathin QWs. Specifically, the analysis involved photoluminescence measurements combined with effective bandgap simulation, x-ray diffraction, and transmission electron microscopy characterization. By controlling the growth temperature, indium content depth profile modifications were achieved for the In(Ga)As/GaAs QWs, leading to substantial changes in the emission properties. The analysis was supported by the effective bandgap simulation, which allowed not only to probe the exact shape of the indium depth profile but also to predict and design the structures with the desired optical characteristics. In the case of In(Ga)N/GaN ultrathin QWs, the growth temperature change affected the total indium incorporation within the QW. Further analysis suggested that the total amount of indium is the dominant factor when dealing with optical emission from ultrathin QWs. The ultimate goal of this research was to characterize, understand, and control ultrathin QW structures in various applications.

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