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HL: Halbleiterphysik

HL 9: Poster I

HL 9.102: Poster

Montag, 27. März 2006, 15:15–17:45, P3

Characterization of AlGaN/GaN - heterostructures by means of magnetotransport measurements in high magnetic fields — •K. Knese¹, F. Vogt¹, N. Riedel¹, U. Rossow¹, E. Sagol², Ch. Stellmach¹, and G. Nachtwei¹ — ¹Institut für Angewandte Physik, Technische Universität Braunschweig, Mendelsohnstr. 2, D-38106 Braunschweig — ²Physikalisch Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

The group-III-nitrides are very promising materials in terms of high power, high temperature and high frequency electronic applications. In this work, we investigate the electronic properties of a two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures grown on sapphire substrates in order to obtain a better understanding of scattering mechanisms and transport properties. Therefore, Shubnikov-de Haas (SdH)- and Hall-measurements were performed on several samples (in Hall bar- and Van der Pauw- geometry) with different Al-content of the AlGaN-barrier in high magnetic fields up to 18 T. From SdH- and Hall- measurements the sheet carrier concentration was determined to be 4·10¹² - 1·10¹³ cm⁻². The analysis of temperature-dependent SdH-oscillations yields an electronic effective mass of 0.23 - 0.26 m₀. In addition, the quantum scattering lifetime τ_t, which is related to the Landau level broadening, and the classical lifetime τ_D can be calculated from such measurements, whereas the ratio τ_t/τ_D is an indicator of the type of scattering mechanism present in the sample. Finally, the effective Landé-factor g^* was determined from angular dependent SdH-measurements.