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Investigation of deep level defects in GaN:C, GaN:Mg and pseudomorphic AlGaN/GaN films

Armstrong, Andrew M

Abstract Details

2006, Doctor of Philosophy, Ohio State University, Electrical Engineering.
GaN-based electronics have a high defect density that impedes device performance. This dissertation investigates the origin of deep levels in GaN and AlGaN/GaN with emphasis on component layers in heterojunction field effect transistors (HFETs). To elucidate the origin of deep levels, spectroscopic techniques were employed to track deep level incorporation as a function of growth methods, growth conditions, doping levels, and Al mole fraction. Techniques were devised for quantitative analysis of deep level concentrations in wide bandgap, semi-insulating semiconductors, and discernment of the deep level spectrum of a nanoscale, pseudomorphic AlGaN layers grown on much thicker GaN films. In GaN:C, which find application as resistive buffers in AlGaN/GaN HFETs, deep states at Ec–3.0 and Ec–3.28 eV were identified with carbon. The deep level at Ec–3.0 eV was associated with a carbon-related yellow luminescence band at 2.2 eV through application of a configuration-coordinate model. The site selectivity of carbon and mechanism for semi-insulating behavior in GaN:C:Si films was observed to depend on substrate temperature of films grown by molecular beam epitaxy. Deep levels in p-type GaN:Mg were found near both band edges, wtih major levels at Ev+3.05, 3.22 and 3.27 eV, and the Ev+3.27 eV state was attributed to residual carbon. Additional states were evident at Ec–2.97 and 3.24 eV, and the latter was attributed to MgGa itself. Methods were established for discriminating the deep level spectra of pseudomorphic, nanoscale AlGaN layers grown upon much thicker GaN films. Deep levels at Ec-2.00 and Ec–3.85 eV were associated with the AlGaN layer while other deep levels at Ec–2.65 and Ec–3.30 eV were attributed to the underlying GaN. Near-Ev bandgap states in were evident in all AlGaN/GaN films, and appear prototypic for Al mole fraction 0<x<0.21. Current-mode measurements applicable to HFET devices were employed. Investigation found a near-Ev bandgap state associated with the AlGaN layer. Further, despite the inclusion of a SI GaN:C buffer in the HFET device, no carbon-related deep level signatures were observed. This demonstrates that a properly tailored growth can incorporate GaN:C in an HFET without deleterious effects.
Steven Ringel (Advisor)
237 p.

Recommended Citations

Citations

  • Armstrong, A. M. (2006). Investigation of deep level defects in GaN:C, GaN:Mg and pseudomorphic AlGaN/GaN films [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1164038818

    APA Style (7th edition)

  • Armstrong, Andrew. Investigation of deep level defects in GaN:C, GaN:Mg and pseudomorphic AlGaN/GaN films. 2006. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1164038818.

    MLA Style (8th edition)

  • Armstrong, Andrew. "Investigation of deep level defects in GaN:C, GaN:Mg and pseudomorphic AlGaN/GaN films." Doctoral dissertation, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1164038818

    Chicago Manual of Style (17th edition)