Doctor of Philosophy, The Ohio State University, 2024, Electrical and Computer Engineering

Contactless, nondestructive measurements of minority carrier lifetime by transient microwave reflectance (TMR) and photoluminescence are used to study the carrier dynamics of several ternary materials: InGaAs, GaAsSb, and InAsSb. As contactless measurements, TMR and photoluminescence can determine quality of as-grown wafers. The minority carrier lifetime is inversely proportional to the diffusion component of the dark current and can be used as an indicator of device performance, without the need for full device fabrication. The ability to yield useful information about wafer quality without the time and cost used for fabrication allows for quick feedback to growers. GaAsSb and InGaAs lattice-matched to InP are candidates for short-wave infrared (SWIR) detection at 1.5 μm, a wavelength used for eye safety and optical communication. The high speed or low signal applications at this wavelength benefit from the use of separate absorber, charge, and multiplier (SACM) avalanche photodiodes (APDs). In these devices, the absorber is optimized for detection at the wavelength of interest, and the multiplier is optimized for gain through impact ionization. InGaAs-based SACM APDs are a mature technology and are available commercially. The multipliers paired with InGaAs, however, typically have high noise. Research into low-noise multipliers has resulted in the demonstration of AlGaAsSb as a low noise material. When AlGaAsSb is paired with InGaAs, the grading material AlInGaAs creates a conduction band offset with AlGaAsSb, limiting bandwidth. GaAsSb lattice-matched to InP has similar properties to InGaAs and could be implemented without a conduction band offset due to the grading material being AlGaAsSb. When a GaAsSb/AlGaAsSb SACM APD was demonstrated, it was found to have higher dark current than commercial InGaAs-based devices. Because these materials are so similar, this was unexpected. As mentioned, the diffusion component of the dark current is inversely proportio (open full item for complete abstract)

Committee: Sanjay Krishna (Advisor); Steve Ringel (Committee Member); Preston Webster (Committee Member); Anant Agarwal (Committee Member); Shamsul Arafin (Committee Member) Subjects: Electrical Engineering

BA, Oberlin College, 1968, Geology

The work of this project was divided between analytical chemistry by xray fluorescence techniques and geologic interpretation of a series of PreCambrian crystalline rocks from the contact aureole of the Stillwater igneous complex in the Beartooth Mts. of Montana. The former was needed for the latter. There are two sections to the report which correspond to the double thrust of the research.The purpose of this section of the paper is to document the xray fluorescence methods used to obtain the data reported on Rb, Sr, Fe, Mn, and Ti concentration values in a later section of the paper. Also, a new instrumental approach and a new analytical method are suggested for the analyses of the elements of atomic number 21-26 (Sc-Fe). All methods involve estimation of the mass absorption coefficient (μ) of the rock.

Committee: William Skinner (Advisor); James Powell (Advisor) Subjects: Chemistry; Geology

Master of Science (MS), Wright State University, 2012, Physics

An optical material parameter predictive model that accounts for sample to air interfaces was developed. The model predicts how a terahertz time-domain spectroscopy time domain pulse will be affected as it passes through a given thickness of a material. The model assumes a homogenous, linear, isotropic dielectric or semiconductor. The inputs to the model are the real and imaginary refractive indices across the desired frequency band. Different dielectric material's optical parameters were taken from the literature and the predicted time domain pulses were shown. It was also shown that the refractive index and absorption coefficient for samples that were optically thick and low-loss could be determined from measurements analytically. It was also shown that for non-dispersive media with a flat absorption coefficient, the predictive model could be used to determine an average value for both the index of refraction and the absorption coefficient across the frequency band, (0.1-4 terahertz).

Committee: Jason Deibel PhD (Advisor); Douglas Petkie PhD (Committee Member); Gregory Kozlowski PhD (Committee Member) Subjects: Physics