Dislocation-governed current-transport mechanism in (Ni/Au)–AlGaN/AlN/GaN heterostructures

Abstract

The current-transport mechanisms in ͑Ni/ Au͒ -Al 0,22 Ga 0,78 N / AlN/ GaN heterostructures were studied by using temperature dependent forward-bias current-voltage ͑I-V͒ characteristics in the temperature range of 80-410 K. In order to determine the current mechanisms for ͑Ni/ Au͒ -Al 0,22 Ga 0,78 N / AlN/ GaN heterostructures, we fitted the experimental I-V data to the analytical expressions given for the current-transport mechanisms in a wide range of applied biases and at different temperatures. The contributions of thermionic-emission, generation-recombination, tunneling, leakage currents that are caused by inhomogeneities, and defects at the metal-semiconductor interface current mechanisms were all taken into account. The best fitting results were obtained for the tunneling current mechanism. On the other hand, we did not observe sufficient agreement between the experimental data and the other current mechanisms. The temperature dependencies of the tunneling saturation current ͑I t ͒ and tunneling parameters ͑E 0 ͒ were obtained from fitting results. We observed a weak temperature dependence of the saturation current and the absence of the temperature dependence of the tunneling parameters in this temperature range. The results indicate that in the temperature range of 80-410 K, the mechanism of charge transport in the ͑Ni/ Au͒ −Al 0.22 Ga 0.78 N / AlN/ GaN heterostructure is performed by tunneling among those dislocations intersecting the space charge region. The dislocation density ͑D͒ that was calculated from the I-V characteristics, according to a model of tunneling along the dislocation line, gives the value of 0.24ϫ 10 7 cm −2 . This value is close in magnitude to the dislocation density that was obtained from the x-ray diffraction measurements.

Leakage current by Frenkel–Poole emission in Ni/Au Schottky contacts on Al0.83In0.17N/AlN/GaN heterostructures

“…6,7,15 The threading dislocation density for the GaN based high electron mobility transistor structures grown on sapphire substrate are given on the order of 10 8 cm −2 . 12 The dislocation density for Al 0.83 In 0.17 N / AlN/ GaN heterostructure were measured as 5.9ϫ 10 8 cm −2 in this study. Measuring the emission barrier height of 0.12 eV would require the relevant trapped state to be located 0.12 eV below the conduction-band edge of Al 0.83 In 0.17 N. 7 The electric field and temperature dependence of the current density dictates the Frenkel-Poole emission rather than Schottky emission, in which carrier transport from the metal contact into the conductive dislocation must occur via a trapped state rather than by direct thermionic emission from the metal.…”

“…[4][5][6]12 In the case of dominant dislocation-related conductivity in the leakage current at room temperature for Al 0.83 In 0.17 N / AlN/ GaN Schottky diodes, we required in our analysis that a single transport mechanism must accurately describe the current flow. The transport model based on Frenkel-Poole emission satisfied this criterion and gives realistic values for the necessary physical parameters.…”

“…Also, the dislocation density of the Al 0.83 In 0.17 N / AlN/ GaN heterostructure sample was determined as 5.9ϫ 10 8 cm −2 by the methods of high-resolution x-ray diffraction. 12 The current-voltage ͑I-V͒ measurements were performed by the use of an HP 4145 semiconductor parameter analyzer in a temperature range of 250-375 K by using a temperature controlled close-cycle helium cryostat. The sample temperature was monitored by using a copper-constantan thermocouple that was close to the sample and measured with Lake Fig.…”

The effect of insulator layer thickness on the main electrical parameters in (Ni/Au)/AlxGa1−xN/AlN/GaN heterostructures

“…[1 -9] In recent years high dielectric materials have been proposed for application as an insulator layer at the metal/semiconductor (M/S) interface such as a metal-TiO 2 -semiconductor (MIS or MOS), metal-Bi 3 Ti 4 O 12 -semiconductor (MFS) structures, and high electron mobility transistors (HEMTs). [10] In addition, there are various nonidealities in these structures, such as the formation of an insulator layer at the M/S interface, the energy distribution profile of N ss at the semiconductor/insulator (S/I) interface, R s , and inhomogeneous barrier heights (BHs). The values of N ss and R s of these devices are important parameters that affect both I-V and C-V characteristics.…”

“…heterostructures can be seen in our previous study. [10] After the formation of the ohmic contact, the SiN x layer was deposited by plasma-enhanced chemical vapor deposition (PECVD) on …”