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Quantitative defect spectroscopy on operating AlGaN/GaN high electron mobility transistors

Malonis, Andrew C.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1259597046

Abstract Details

2009, Master of Science, Ohio State University, Electrical and Computer Engineering.
Despite numerous advances in the growth, fabrication, and characterization of AlGaN/GaN HEMT devices, there remain a number of unknowns related to the impact of deep levels on HEMT performance. Of specific interest to ongoing development of HEMT technology is the development of techniques which can not only detect the specific energy levels of deep levels in operating devices, but can also relate the presence of these defects to changes in specific device parameters. By examining more established techniques and developing new on-device characterization methods, the impact of defects on AlGaN/GaN HEMTs was quantitatively studied. Constant-voltage measurements of current and conductance transients are applied to AlGaN/GaN HEMT devices. Current deep level transient spectroscopy revealed two levels, one with an apparent activation energy that ranged from 0.16 eV to 0.31 eV, and one with an activation energy of 0.52 eV. The manifestation of both of these levels was shown to be affected by the magnitude of the gate-drain electric field. Conductance deep level transient spectroscopy reveled a number of traps with energies between EC- 0.20 eV and EC-0.42 eV, with the presence of a complex field profile making it difficult to determine which peaks were due to unique defects and which were due to the same species of defect emitting under multiple field conditions. Current deep level optical spectroscopy and conductance deep level optical spectroscopy were used to identify various deep levels with onsets at EC-1.55 eV, EC-2.55 eV, EC-2.9 eV, EC-3.25 eV, and EC-3.8 eV. These levels were similar to deep levels previously identified by capacitance measurements on similar material. None of these measurements yielded either trap concentrations or the impact of deep levels on parameters. To facilitate quantitative examination of the effect of deep levels on device parameters, the theory of constant-current measurements is developed. By regulating either the drain or gate voltage to maintain a constant drain current, the impact of deep levels on either drain resistance or threshold voltage can be observed. To showcase these techniques, the impact of SiN passivation on AlGaN/GaN HEMTs is studied. Drain controlled constant-current deep level transient spectroscopy reveled a deep level at EC-0.42 eV, whose signal was lower by a factor of 4 in passivated vs. unpassivated devices, proving that the technique is sensitive to changes in the device access region. Drain-controlled constant-current deep level optical spectroscopy reveled steady-state onsets in the drain resistance at incident photon energies of 1.3 eV, 2.3 eV, and 3.7 eV, similar to energies observed in similar material. The signal from these deep levels was decreased by a factor of approximately 4 by the presence of SiN passivation, again confirming access region sensitivity.
Steven A. Ringel, PhD (Advisor)
Siddharth Rajan, PhD (Committee Member)
142 p.
Electrical Engineering; Materials Science
GaN; AlGaN; HEMT; defect; trap; deep level; spectroscopy; DLTS; DLOS; ID-DLTS; ID-DLOS; CID-DLTS; CID-DLOS

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Citations

  • Malonis, A. C. (2009). Quantitative defect spectroscopy on operating AlGaN/GaN high electron mobility transistors [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259597046

    APA Style (7th edition)

  • Malonis, Andrew. Quantitative defect spectroscopy on operating AlGaN/GaN high electron mobility transistors. 2009. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1259597046.

    MLA Style (8th edition)

  • Malonis, Andrew. "Quantitative defect spectroscopy on operating AlGaN/GaN high electron mobility transistors." Master's thesis, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259597046

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.