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Correlation between Sheet Carrier Density-Mobility Product and Persistent Photoconductivity in ALGAN/GAN Modulation Doped Heterostructures

Published online by Cambridge University Press:  03 September 2012

J. Z. Li ,
J. Li ,
J. Y. Lin  and
H. X. Jiang
J. Z. Li
Affiliation:
Department of Physics, Kansas State UniversityManhattan, KS 66506-2601
J. Li
Affiliation:
Department of Physics, Kansas State UniversityManhattan, KS 66506-2601
J. Y. Lin
Affiliation:
Department of Physics, Kansas State UniversityManhattan, KS 66506-2601
H. X. Jiang
Affiliation:
Department of Physics, Kansas State UniversityManhattan, KS 66506-2601
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Abstract

High quality Al0.25Ga0.75N/GaN modulation-doped heterojunction field-effect transistor (MOD-HFET) structures grown on sapphire substrates with high sheet carrier density and mobility products (nsμ > 1016/Vs at room temperature) have been grown by metal organic chemical vapor deposition (MOCVD). The optimized structures were achieved by varying structural parameters, including the AlGaN spacer layer thickness, the Si-doped AlGaN barrier layer thickness, the Si-doping concentration, and the growth pressure. In these structures, the persistent photoconductivity (PPC) effect associated with the two-dimensional electron gas (2DEG) system was invariantly observed. As a consequence, the characteristic parameters of the 2DEG were sensitive to light and the sensitivity was associated with permanent photoinduced increases in the 2DEG carrier mobility (μ) and sheet carrier density (ns). However, we observed that the magnitude of the PPC and hence the photoinduced instability associated with these heterostructures were a strong function of only one parameter, the product of ns and μ, which is the most important parameter for the HFET device design. For a fixed excitation photon dose, the ratio of the low temperature PPC to the dark conductivity level was observed to decrease from 200% to 3% as the nsμ (300 K) product was increased from 0.048 × 1016/Vs to 1.4 ‘times; 1016/Vs. Based on our studies, we suggest that the magnitude of the low temperature PPC can be used as a sensitive probe for monitoring the electronic quality of the AlGaN/GaN HFET structures.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 595: Symposium W – GaN and Related Alloys - 1999 , 1999 , F99W11.12
Copyright
Copyright © Materials Research Society 1999

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