Correlation between sheet carrier density-mobility product and persistent photoconductivity in AlGaN/GaN modulation doped heterostructures
High quality Al{sub 0.25}Ga{sub 0.75}N/GaN modulation-doped heterojunction field-effect transistor (MOD-HFET) structures grown on sapphire substrates with high sheet carrier density and mobility products (n{sub s}{mu} > 10{sup 16}/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 (mu) and sheet carrier density (n{sub s}). However, the authors 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 n{sub s} and {mu}, 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 n{sub s}{mu} (300 K) product was increased from 0.048 x 10{sup 16}/Vs to 1.4 x 10{sup 16}/Vs. Based on their studies, the authors 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.
- Research Organization:
- Kansas State Univ., Manhattan, KS (US)
- OSTI ID:
- 20104598
- Resource Relation:
- Conference: 1999 Materials Research Society Fall Meeting, Boston, MA (US), 11/28/1999--12/03/1999; Other Information: PBD: 2000; Related Information: In: GaN and related alloys -- 1999. Materials Research Society symposium proceedings, Volume 595, by Myers, T.H.; Feenstra, R.M.; Shur, M.S.; Amano, Hiroshi [eds.], [1050] pages.
- Country of Publication:
- United States
- Language:
- English
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