Browsing by Subject "Double channel"

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    Current-Transport mechanisms in the AlInN/AlN/GaN single-channel and AlInN/AlN/GaN/AlN/GaN double-channel heterostructures
    (Elsevier, 2013) Arslan, E.; Turan, S.; Gökden, S.; Teke, A.; Özbay, Ekmel
    Current-transport mechanisms were investigated in Schottky contacts on AlInN/AlN/GaN single channel (SC) and AlInN/AlN/GaN/AlN/GaN double channel (DC) heterostructures. A simple model was adapted to the current-transport mechanisms in DC heterostructure. In this model, two Schottky diodes are in series: one is a metal-semiconductor barrier layer (AIInN) Schottky diode and the other is an equivalent Schottky diode, which is due to the heterojunction between the AlN and GaN layer. Capacitance-voltage studies show the formation of a two-dimensional electron gas at the AlN/GaN interface in the SC and the first AlN/GaN interface from the substrate direction in the DC. In order to determine the current mechanisms for SC and DC heterostructures, we fit the analytical expressions given for the tunneling current to the experimental current-voltage data over a wide range of applied biases as well as at different temperatures. We observed a weak temperature dependence of the saturation current and a fairly small dependence on the temperature of the tunneling parameters in this temperature range. At both a low and medium forward-bias voltage values for Schottky contacts on AlInN/AlN/GaN/AlN/GaN DC and AlInN/AlN/GaN SC heterostructures, the data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations in the temperature range of 80-420 K.
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    ItemOpen Access
    The effect of GaN thickness inserted between two AlN layers on the transport properties of a lattice matched AlInN/AlN/GaN/AlN/GaN double channel heterostructure
    (Elsevier BV, 2014-01-31) Tülek, R.; Arslan, E.; Bayraklı, A.; Turhan, S.; Gökden, S.; Duygulu, Ö.; Kaya, A.; Fırat, T.; Teke, A.; Özbay, Ekmel
    One AlInN/AlN/GaN single channel heterostructure sample and four AlInN/AlN/GaN/AlN/GaN double channel heterostructure samples with different values of the second GaN layer were studied. The interface profiles, crystalline qualities, surface morphologies, and dislocation densities of the samples were investigated using high resolution transmission electron microscopy, atomic force microscopy, and high-resolution X-ray diffraction. Some of the data provided by these measurements were used as input parameters in the calculation of the scattering mechanisms that govern the transport properties of the studied samples. Experimental transport data were obtained using temperature dependent Hall effect measurements (10-300 K) at low (0.5 T) and high (8 T) magnetic fields to exclude the bulk transport from the two-dimensional one. The effect of the thickness of the second GaN layer inserted between two AlN barrier layers on mobility and carrier concentrations was analyzed and the dominant scattering mechanisms in the low and high temperature regimes were determined. It was found that Hall mobility increases as the thickness of GaN increases until 5 nm at a low temperature where interface roughness scattering is observed as one of the dominant scattering mechanisms. When GaN thicknesses exceed 5 nm, Hall mobility tends to decrease again due to the population of the second channel in which the interface becomes worse compared to the other one. From these analyses, 5 nm GaN layer thicknesses were found to be the optimum thicknesses required for high electron mobility. (C) 2013 Published by Elsevier B.V.