Parts | Days | Selection | Search | Updates | Downloads | Help
HL: Fachverband Halbleiterphysik
HL 25: Poster Session: GaN - Optical Properties & Preparation and Characterization & Devices
HL 25.13: Poster
Monday, March 26, 2012, 16:00–19:00, Poster D
Direct determination of piezoelectric coefficients for GaN by AFM — •Uwe Röder1, Frank Lipski2, Martin Feneberg3, Ferdinand Scholz2, and Klaus Thonke1 — 1Institute of Quantum Matter / Semiconductor Physics Group, Ulm University — 2Institute of Optoelectronics, Ulm University — 3Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg
For the piezoelectric coefficients of GaN a broad range can be found in literature (d33 = 2 ... 4 pm/V; d15 = 2.9 ...3.3 pm/V). Mostly, these parameters have been determined from polycrystalline thin layers. We present here data obtained on thick semi-insulating Fe doped GaN layers grown by HVPE. By applying AC voltages with varying amplitude and frequency to top and bottom contacts, and measuring the elongation of the thick GaN layer with an AFM tip in contact mode and lock-in technique to record the phase-correlated periodic change of the quadrature diode signal, we get a direct measure of the piezoelectric constant d33. We obtain a value of d33 = (2.2 ± 0.3) pm/V. Similarly, d15 could be obtained by recording the shear displacement. Effects of mechanical sample resonances etc. have to be carefully avoided.