Deep Traps in AlGaN/GaN Heterostructures Studied by Deep Level Transient Spectroscopy: Effect of Carbon Concentration in GaN Buffer Layers

Authors

Z-Q. Fang
B. Claflin
David C. Look, Wright State University - Main CampusFollow
D. S. Green
R. Vetury

Document Type

Article

Publication Date

9-1-2010

Abstract

Electrical properties, including leakage currents, threshold voltages, and deep traps, of AlGaN/GaN heterostructure wafers with different concentrations of carbon in the GaN buffer layer, have been investigated by temperature dependent current-voltage and capacitance-voltage measurements and deep level transient spectroscopy (DLTS), using Schottky barrier diodes (SBDs). It is found that (i) SBDs fabricated on the wafers with GaN buffer layers containing a low concentration of carbon (low-[C] SBD) or a high concentration of carbon (high-[C] SBD) have similar low leakage currents even at 500 K; and (ii) the low-[C] SBD exhibits a larger (negative) threshold voltage than the high-[C] SBD. Detailed DLTS measurements on the two SBDs show that (i) different trap species are seen in the two SBDs: electron traps A_x (0.9 eV), A₁ (0.99 eV), and A₂ (1.2 eV), and a holelike trap H₁ (1.24 eV) in the low-[C] SBD; and electron traps A₁, A₂, and A₃ ( ∼ 1.3 eV), and a holelike trap H₂ (>1.3 eV) in the high-[C] SBD; (ii) for both SDBs, in the region close to GaN buffer layer, only electron traps can be detected, while in the AlGaN/GaN interface region, significant holelike traps appear; and iii) all of the deep traps show a strong dependence of the DLTS signal on filling pulse width, which indicates they are associated with extended defects, such as threading dislocations. However, the overall density of electron traps is lower in the low-[C] SBD than in the high-[C] SBD. The different traps observed in the two SBDs are thought to be mainly related to differences in microstructure (grain size and threading dislocation density) of GaN buffer layers grown at different pressures.

Comments

Copyright © 2010, American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in the Journal of Applied Physics 108.6, and may be found at http://jap.aip.org/resource/1/japiau/v108/i6/p063706_s1

Repository Citation

Fang, Z., Claflin, B., Look, D. C., Green, D. S., & Vetury, R. (2010). Deep Traps in AlGaN/GaN Heterostructures Studied by Deep Level Transient Spectroscopy: Effect of Carbon Concentration in GaN Buffer Layers. Journal of Applied Physics, 108 (6), 63706.
https://corescholar.libraries.wright.edu/physics/166

DOI

10.1063/1.3488610