Date of Graduation

12-2019

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Graduate School

Advisor

Morgan Ware

Committee Member

Cynthia Sides

Second Committee Member

Zhong Chen

Third Committee Member

Rick Wise

Keywords

solar cells, renewable energy, energy band gaps, nitride semiconductors, LEDs

Abstract

III-nitride materials have recently attracted much attention for applications in both the microelectronics and optoelectronics. For optoelectronic devices, III-nitride materials with tunable energy band gaps can be used as the active region of devices to enhance the absorption or emission. A such material is indium nitride (InN), which along with gallium nitride (GaN) and aluminum nitride (AlN) embody the very real promise of forming the basis of a broad spectrum, a high efficiency solar cell. One of the remaining complications in incorporating InN into a solar cell design is the effects of the high temperature growth of the GaN crystal on the InN crystal, which begins to degrade at these high temperatures over approximately 500 °C.

Two samples of GaN/sapphire substrates were utilized to grow InN layers with different thickness, 300 nm and 1000 nm, and temperature, 450 °C and 400 °C, by molecular beam epitaxy, respectively. These samples were explored using atomic force microscopy, scanning electron microscopy, and optical microscopy to characterize the surface defects, and x-ray diffraction, transmission measurements, and Raman to characterize the structure defects. After studying the two samples, the 1000 nm InN layer with a growth temperature of 400 °C had a high-quality crystal structure and good surface morphology compared with the 300 nm InN layer with a growth temperature of 450 °C.

The 1000 nm InN layer with a growth temperature of 400 °C was used as a substrate to study the growth of GaN on InN. This was initiated with a cap of 10 nm GaN at 400 °C to prevent the InN from evaporating. Then, a 50 nm layer of GaN was grown at high temperature (795 °C). After characterizing the surface morphology and the quality of crystal structure, the GaN layer was very rough, and the InN layer was found to have evaporated completely during the growth process. Therefore, another sample was grown with 50 nm GaN at low temperature, 400 °C. After characterizing the crystal structure and surface morphology, the GaN layer was successfully deposited on the InN layer.

Available for download on Wednesday, December 16, 2020

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