Epitaxy of boron phosphide on AIN, 4H-SiC, 3C-SiC and ZrB₂ substrates

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dc.contributor.author Padavala, Balabalaji
dc.date.accessioned 2016-07-07T13:53:51Z
dc.date.available 2016-07-07T13:53:51Z
dc.date.issued 2016-08-01 en_US
dc.identifier.uri http://hdl.handle.net/2097/32808
dc.description.abstract The semiconductor boron phosphide (BP) has many outstanding features making it attractive for developing various electronic devices, including neutron detectors. In order to improve the efficiency of these devices, BP must have high crystal quality along with the best possible electrical properties. This research is focused on growing high quality crystalline BP films on a variety of superior substrates like AIN, 4H-SiC, 3C-SiC and ZrB₂ by chemical vapor deposition. In particular, the influence of various parameters such as temperature, reactant flow rates, and substrate type and its crystalline orientation on the properties of BP films were studied in detail. Twin-free BP films were produced by depositing on off-axis 4H-SiC(0001) substrate tilted 4° toward [1-100] and crystal symmetry matched zincblende 3C-SiC. BP crystalline quality improved at higher deposition temperature (1200°C) when deposited on AlN, 4H-SiC, whereas increased strain in 3C-SiC and increased boron segregation in ZrB₂ at higher temperatures limited the best deposition temperature to below 1200°C. In addition, higher flow ratios of PH₃ to B₂H₆ resulted in smoother films and improved quality of BP on all substrates. The FWHM of the Raman peak (6.1 cm⁻¹), XRD BP(111) peak FWHM (0.18°) and peak ratios of BP(111)/(200) = 5157 and BP(111)/(220) = 7226 measured on AlN/sapphire were the best values reported in the literature for BP epitaxial films. The undoped films on AlN/sapphire were n-type with a highest electron mobility of 37.8 cm²/V·s and a lowest carrier concentration of 3.15x1018 cm⁻ᶟ. Raman imaging had lower values of FWHM (4.8 cm⁻¹) and a standard deviation (0.56 cm⁻¹) for BP films on AlN/sapphire compared to 4H-SiC, 3C-SiC substrates. X-ray diffraction and Raman spectroscopy revealed residual tensile strain in BP on 4H-SiC, 3C-SiC, ZrB₂/4H-SiC, bulk AlN substrates while compressive strain was evident on AlN/sapphire and bulk ZrB₂ substrates. Among the substrates studied, AlN/sapphire proved to be the best choice for BP epitaxy, even though it did not eliminate rotational twinning in BP. The substrates investigated in this work were found to be viable for BP epitaxy and show promising potential for further enhancement of BP properties. en_US
dc.description.sponsorship 1) U.S. Department of Energy - grant nos. DE-SC000516, GEGF001846 and DE-AC02-98CH10886. 2) National Science Foundation - grant no. EPSCoR IIA-1430493. en_US
dc.language.iso en_US en_US
dc.publisher Kansas State University en
dc.subject Semiconducting III-V materials en_US
dc.subject Boron phosphide en_US
dc.subject Chemical vapor deposition en_US
dc.subject Hydride vapor phase epitaxy en_US
dc.subject Characterization en_US
dc.title Epitaxy of boron phosphide on AIN, 4H-SiC, 3C-SiC and ZrB₂ substrates en_US
dc.type Dissertation en_US
dc.description.degree Doctor of Philosophy en_US
dc.description.level Doctoral en_US
dc.description.department Department of Chemical Engineering en_US
dc.description.advisor James H. Edgar en_US
dc.date.published 2016 en_US
dc.date.graduationmonth August en_US


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