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University of Rochester

1. Kohnke, Glenn E. (1967 - ). Emission, gain, and absorption in n-type modulation doped quantum well laser diodes.

Degree: PhD, 2017, University of Rochester

The properties of n-type modulation doped lasers grown by molecular beam epitaxy are investigated with regard to emission, gain, and absorption. This study employs constant and stepped core doping profiles in single quantum well separate confinement heterostructure lasers. The design, characterization, and fabrication of lasers is presented. Constant core doping lasers are found to have a prohibitively large increase in threshold current density associated with a shift in lasing wavelength to shorter wavelengths with increased doping. Electroluminescence spectra suggest the increase in threshold current density is related to both nonradiative and below bandgap radiative transitions present in heavily doped material. Stepped core doping lasers exhibit a shift to shorter wavelength attributed to second quantized state lasing with increased doping density and show only a slight increase in the associated threshold current density. The differences between photoluminescence and emission obtained from electrical injection are discussed. To further examine the mechanism of the wavelength shift in the stepped core lasers, the gain spectra are measured as a function of injected current. Modulation doped lasers are found to have wider gain spectra than undoped core lasers. The low current spectra provide a measurement of absorption at the lasing wavelength which is used to examine the 2D Burstein-Moss shift in these devices. The modulation doped devices have lower absorption coefficients at the lasing wavelength by a factor of two as compared to undoped core lasers. Due to the lack of an exciton feature in the lightly pumped gain spectrum of the undoped core reference laser, it is postulated that the quantum well contains unintentional dopants caused by Beryllium (Be) diffusion during growth. Photoluminescence absorption spectroscopy is presented as a rapid analytical tool for determining the presence of Be in the quantum well of laser structures. Results are confirmed by measuring hole concentrations with capacitance-voltage profiling and Be concentrations with secondary ion mass spectroscopy. The growth conditions are optimized to reduce the Be diffusion. The gain spectra of an improved undoped laser are measured and compared with previous results.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Kohnke, G. E. (. -. ). (2017). Emission, gain, and absorption in n-type modulation doped quantum well laser diodes. (Doctoral Dissertation). University of Rochester. Retrieved from http://hdl.handle.net/1802/32172

Chicago Manual of Style (16th Edition):

Kohnke, Glenn E (1967 - ). “Emission, gain, and absorption in n-type modulation doped quantum well laser diodes.” 2017. Doctoral Dissertation, University of Rochester. Accessed December 18, 2017. http://hdl.handle.net/1802/32172.

MLA Handbook (7th Edition):

Kohnke, Glenn E (1967 - ). “Emission, gain, and absorption in n-type modulation doped quantum well laser diodes.” 2017. Web. 18 Dec 2017.

Vancouver:

Kohnke GE(-). Emission, gain, and absorption in n-type modulation doped quantum well laser diodes. [Internet] [Doctoral dissertation]. University of Rochester; 2017. [cited 2017 Dec 18]. Available from: http://hdl.handle.net/1802/32172.

Council of Science Editors:

Kohnke GE(-). Emission, gain, and absorption in n-type modulation doped quantum well laser diodes. [Doctoral Dissertation]. University of Rochester; 2017. Available from: http://hdl.handle.net/1802/32172

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