Electromechanical coupling in free-standing AlGaN/GaN planar structures

Abstract

This work, resulting from Air Force contract F33615-00-C-5402, is copyrighted. The United States has for itself and other acting on its behalf and unlimited, paid-up, nonexclusive, irrevocable worldwide license. Any other form of use is subject to copyright restrictions. MATERIALS AND MANUFACTURING DIRECTORATE AIR FORCE RESEARCH LABORATORY AIR FORCE MATERIEL COMMAND WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750Approved for public release; distribution is unlimited. /m M./7^N/«M ■m\ ^ »■* u.->«e^ NOTICE Using government drawings, specifications, or other data included in this document for any purpose other than government procurement does not in any way obligate the U.S. Government. The fact that the government formulated or supplied the drawings, specifications, or other data does not license the holder or any other person or corporation; or convey any rights or permission to manufacture, use, or sell any patented invention that may relate to them. This report has been reviewed by the AFRL Wright Site Office of Public Affairs (WS/PA) and is relcasable to the National Technical Information Service (NTIS). At NTIS, it will be available to the general public, including foreign nationals.This technical report has been reviewed and is approved for publication. The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-ML-WP-TP-2004-403 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES© 2003 American Institute of Physics. This work, resulting from Air Force contract F33615-00-C-5402, is copyrighted. The United States has for itself and other acting on its behalf and unlimited, paid-up, nonexclusive, irrevocable worldwide license. Any other form of use is subject to copyright restrictions. ABSTRACT (Maximum 200 Words), ,The strain and electric fields present in free-standing AlGaN/GaN slabs are examined theoretically within the framework of fully coupled continuum elastic and dielectric models. Simultaneous solutions for the electric field and strain components are obtained by minimizing the electric enthalpy. We apply constraints appropriate to pseudomorphic semiconductor epitaxial layers and obtain closed-form analytic expressions that take into account the wurtzite crystal anisotropy. It is shown that in the absence of free charges, the calculated strain and electric fields are substantially different from those obtained using the standard model without electromechanical coupling. It is also shown, however, that when a two-dimensional electron gas is present at the AlGaN/GaN interface, a condition t...

On the possibility of sub 60 mV/decade subthreshold switching in piezoelectric gate barrier transistors

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Effect of Nonlinear Elasticity on Interband and Intersubband Transition Energies in GaN/AlN Superlattices

“…(1) takes into account the effect of the nonlinear elasticity since the elastic constants are pressure-dependent. The second term on the right hand side of this equation describes the converse piezoelectric effect and it is responsible for the electromechanical coupling effect [4][5][6]. The intrinsic hydrostatic pressure P int , originating from the lattice misfit between constituents of a SL, equals P int = − 2 3 σ ⊥ [10].…”

“…Due to the presence of large internal strains and piezoelectric fields in these structures, the conventional linear theories of elasticity and piezoelectricity have turned out to be insufficient [1][2][3][4][5][6][7][8][9][10]. Recently, higher order electromechanical effects, including the nonlinear piezoelectricity [1][2][3], electromechanical coupling [4][5][6], and nonlinear elasticity [7][8][9][10] have been studied in nitride semiconductors and their heterostructures.…”

Bias induced strain in AlGaN∕GaN heterojunction field effect transistors and its implications

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“…[2][3][4] With both AlGaN and GaN being rather strong piezoelectric materials a more complete approach would use fully coupled electromechanical equations to relate stress to the electric field as well as to the strain in these systems. 5 In this letter, we apply the fully coupled equations to the AlGaN / GaN HFET. The coupled formulation results in piezoelectric polarization charge that is 6.0% lower than the simplified uncoupled model for the technologically important Al 0.3 Ga 0.7 Al/ GaN structure.…”