Browsing by Subject "Parallel conduction"

Now showing 1 - 4 of 4

Open Access
Investigation of low-temperature electrical conduction mechanisms in highly resistive GaN bulk layers extracted with Simple Parallel Conduction Extraction Method
(Springer, 2009-12-03) Yildiz, A.; Lisesivdin, S. B.; Kasap, M.; Ozcelik, S.; Özbay, Ekmel; Balkan, N.
The electrical conduction mechanisms in various highly resistive GaN layers of Al x Ga1-x N/AlN/GaN/AlN heterostructures are investigated in a temperature range between T=40 K and 185 K. Temperature-dependent conductivities of the bulk GaN layers are extracted from Hall measurements with implementing simple parallel conduction extraction method (SPCEM). It is observed that the resistivity (ρ) increases with decreasing carrier density in the insulating side of the metal-insulator transition for highly resistive GaN layers. Then the conduction mechanism of highly resistive GaN layers changes from an activated conduction to variable range hopping conduction (VRH). In the studied temperature range, ln∈(ρ) is proportional to T -1/4 for the insulating sample and proportional to T -1/2 for the more highly insulating sample, indicating that the transport mechanism is due to VRH.
Open Access
Scattering analysis of two-dimensional electrons in AlGaN/GaN with bulk related parameters extracted by simple parallel conduction extraction method
(American Institute of Physics, 2010-07-15) Lisesivdin, S. B.; Yildiz, A.; Balkan, N.; Kasap, M.; Ozcelik, S.; Özbay, Ekmel
We carried out the temperature (22-350 K) and magnetic field (0.05 and 1.4 T) dependent Hall mobility and carrier density measurements on Al 0.22Ga0.78N/GaN heterostructures with AlN interlayer grown by metal-organic chemical-vapor deposition. Hall data is analyzed with a simple parallel conduction extraction method and temperature dependent mobility and carrier densities of the bulk and two-dimensional (2D) electrons are extracted successfully. The results for the bulk carriers are discussed using a theoretical model that includes the most important scattering mechanisms that contribute to the mobility. In order to investigate the mobility of two-dimensional electron gas, we used a theoretical model that takes into account the polar optical phonon scattering, acoustic phonon scattering, background impurity scattering, and interface roughness scattering in 2D. In these calculations, the values are used for the deformation potential and ionized impurity density values were obtained from the bulk scattering analysis. Therefore, the number of fitting parameters was reduced from four to two. © 2010 American Institute of Physics.
Open Access
SiC substrate effects on electron transport in the epitaxial graphene layer
(Springer, 2014) Arslan, E.; Çakmakyapan S.; Kazar, Ö.; Bütün, S.; Lişesivdin, S. B.; Cinel, N. A.; Ertaş, G.; Ardalı, Ş.; Tıraş, E.; Jawad-ul-Hassan,; Özbay, Ekmel; Janzén, E.
Hall effect measurements on epitaxial graphene (EG) on SiC substrate have been carried out as a function of temperature. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the EG layers and within the underlying SiC substrate are readily separated and characterized by the simple parallel conduction extraction method (SPCEM). Two electron carriers are identified in the EG/SiC sample: one highmobility carrier (3493 cm2 /Vs at 300 K) and one low-mobility carrier (1115 cm2 /Vs at 300 K). The high mobility carrier can be assigned to the graphene layers. The second carrier has been assigned to the SiC substrate.
Open Access
A simple parallel conduction extraction method (SPCEM) for MODFETs and undoped GaN-based HEMTs
(ELSEVIER, 2008-07-14) Lisesivdin, S. B.; Balkan, N.; Özbay, Ekmel
We report a simple method to extract the mobility and sheet carrier densities of conduction channels in conventional modulation doped field-effect transistor (MODFET) structures and unintentionally doped GaN-based high-electron mobility transistor (HEMT) structures for a special case. Extraction of the conduction channels from the magnetic field-dependent data can present number of problems; even the most recent methods encounter great difficulties. For the GaN-based HEMT structures which have lower mobilities and larger effective masses than that of GaAs-based counterparts, these difficulties become more prominent. In this study, we describe a simple method for magnetotransport analysis to extract conduction channels successfully for a special case that is commonly encountered: one bulk channel and one two-dimensional electron gas (2DEG) channel. Advantage of this method is mainly its simplicity. The analysis can be done with only two magnetic field-dependent measurements per temperature step. The method is applied to the magnetotransport results of an unintentionally doped AlGaN/AlN/GaN/AlN heterostructure over a temperature range of 29-350 K and in a magnetic field range of 0-1.5 T (μB<1). The results are then compared with those obtained using a commercial package for these calculations namely: quantitative mobility spectrum analysis (QMSA).