Browsing by Subject "Electric resistance"

Now showing 1 - 9 of 9

Open Access
Capacitance-conductance-current-voltage characteristics of atomic layer deposited Au/Ti/Al2O3/n-GaAs MIS structures
(Elsevier Ltd, 2015) Turut, A.; Karabulut, A.; Ejderha, K.; Bıyıklı, Necmi
We have studied the admittance and current–voltage characteristics of the Au/Ti/Al2O3/nGaAs structure. The Al2O3 layer of about 5 nm was formed on the n-GaAs by atomic layer deposition. The barrier height (BH) and ideality factor values of 1.18 eV and 2.45 were obtained from the forward-bias ln I vs V plot at 300 K. The BH value of 1.18 eV is larger than the values reported for conventional Ti/n-GaAs or Au/Ti/n-GaAs diodes. The barrier modification is very important in metal semiconductor devices. The use of an increased barrier diode as the gate can provide an adequate barrier height for FET operation while the decreased barrier diodes also show promise as small signal zero-bias rectifiers and microwave. The experimental capacitance and conductance characteristics were corrected by taking into account the device series resistance Rs. It has been seen that the noncorrection characteristics cause a serious error in the extraction of the interfacial properties. Furthermore, the device behaved more capacitive at the reverse bias voltage range rather than the forward bias voltage range because the phase angle in the reverse bias has remained unchanged as 901 independent of the measurement frequency.
Open Access
Determination of the in-plane effective mass and quantum lifetime of 2D electrons in AlGaN/GaN based HEMTs
(2011) Celik O.; Tiras, E.; Ardali, S.; Lisesivdin, S.B.; Özbay, Ekmel
Magnetoresistance and Hall resistance measurements have been used to investigate the electronic transport properties of AlGaN/GaN based HEMTs. The Shubnikov-de Haas (SdH) oscillations from magnetoresistance, is obtained by fitting the nonoscillatory component to a polynomial of second degree, and then subtracting it from the raw experimental data. It is shown that only first subband is occupied with electrons. The two-dimensional (2D) carrier density and the Fermi energy with respect to subband energy (EF-E1) have been determined from the periods of the SdH oscillations. The in-plane effective mass (m*) and the quantum lifetime (τq) of electrons have been obtained from the temperature and magnetic field dependencies of the SdH amplitude, respectively. The in-plane effective mass of 2D electrons is in the range between 0.19 m0 and 0.22 m0. Our results for in-plane effective mass are in good agreement with those reported in the literature © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Open Access
Electrical characteristics of β-Ga2O3 thin films grown by PEALD
(Elsevier, 2014) Altuntas, H.; Donmez, I.; Ozgit Akgun, C.; Bıyıklı, Necmi
In this work, 7.5 nm Ga2O3 dielectric thin films have been deposited on p-type (1 1 1) silicon wafer using plasma enhanced atomic layer deposition (PEALD) technique. After the deposition, Ga2O 3 thin films were annealed under N2 ambient at 600, 700, and 800 C to obtain β-phase. The structure and microstructure of the β-Ga2O3 thin films was carried out by using grazing-incidence X-ray diffraction (GIXRD). To show effect of annealing temperature on the microstructure of β-Ga2O3 thin films, average crystallite size was obtained from the full width at half maximum (FWHM) of Bragg lines using the Scherrer formula. It was found that crystallite size increased with increasing annealing temperature and changed from 0.8 nm to 9.1 nm with annealing. In order to perform electrical characterization on the deposited films, Al/β-Ga2O3/p-Si metal-oxide- semiconductor (MOS) type Schottky barrier diodes (SBDs) were fabricated using the β-Ga2O3 thin films were annealed at 800 C. The main electrical parameters such as leakage current level, reverse breakdown voltage, series resistance (RS), ideality factor (n), zero-bias barrier height (Bo), and interface states (NSS) were obtained from the current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The RS values were calculated by using Cheung methods. The energy density distribution profile of the interface states as a function of (ESS-EV) was obtained from the forward bias I-V measurements by taking bias dependence of ideality factor, effective barrier height (e), and RS into account. Also using the Norde function and C-V technique, e values were calculated and cross-checked. Results show that β-Ga2O3 thin films deposited by PEALD technique at low temperatures can be used as oxide layer for MOS devices and electrical properties of these devices are influenced by some important parameters such as NSS, RS, and β-Ga2O3 oxide layer.
Open Access
Electronic transport through a kink in an electron waveguide
(Institute of Electrical and Electronics Engineers, 1994) Yalabik, M. C.
The current-voltage denendence correspondinp to electronic transport through a kink in an electronic waveguide is analyzed. No phase breaking dissipation mechanisms are considered, but the effects of the Coulomb interaction are included through a self consistent approximation. The results indicate very nonlinear transport properties, including negative differential resistance and bistability. © 1994 IEEE
Open Access
High performance n-MOSFETs with novel source/drain on selectively grown Ge on Si for monolithic integration
(IEEE, 2009) Yu, H.-Y.; Kobayashi, M.; Jung, W. S.; Okyay, Ali Kemal; Nishi, Y.; Saraswat, K. C.
We demonstrate high performance Ge n-MOSFETs with novel raised source/drain fabricated on high quality single crystal Ge selectively grown heteroepitaxially on Si using Multiple Hydrogen Anealing for Heteroepitaxy(MHAH) technique. Until now low source/drain series resistance in Ge n-MOSFETs has been a highly challenging problem. Source and drain are formed by implant-free, in-situ doping process for the purpose of very low series resistance and abrupt and shallow n+/p junctions. The novel n-MOSFETs show among the highest electron mobility reported on (100) Ge to-date. Furthermore, these devices provide an excellent Ion/Ioff ratio(4× 103) with very high Ion of 3.23μA/μm. These results show promise towards monolithic integration of Ge MOSFETs with Si CMOS VLSI platform.
Open Access
High-Speed InSb photodetectors on GaAs for mid-IR applications
(IEEE, 2004) Kimukin, I.; Bıyıklı, Necmi; Kartaloǧlu, T.; Aytür, O.; Özbay, Ekmel
We report p-i-n type InSb-based high-speed photodetectors grown on GaAs substrate. Electrical and optical properties of photodetectors with active areas ranging from 7.06 × 10 -6 cm 2 to 2.25 × 10 -4 cm 2 measured at 77 K and room temperature. Detectors had high zero-bias differential resistances, and the differential resistance area product was 4.5 Ω cm 2. At 77 K, spectral measurements yielded high responsivity between 3 and 5 μm with the cutoff wavelength of 5.33 μm. The maximum responsivity tor 80-μm diameter detectors was 1.00 × 10 5 V/W at 435 μm while the detectivity was 3.41×10 9 cm Hz 1/2/W. High-speed measurements were done at room temperature. An optical parametric oscillator was used to generate picosecond full-width at half-maximum pulses at 2.5 μm with the pump at 780 mm. 30-μm diameter photodetectors yielded 3-dB bandwidth of 8.5 GHz at 2.5 V bias.
Open Access
Mg-doped AlGaN grown on an AlN/sapphire template by metalorganic chemical vapour deposition
(2006) Yu, H.; Strupinski, W.; Butun, S.; Özbay, Ekmel
The growth of high-performance Mg-doped p-type Al xGa 1-xN (x = 0.35) layers using low-pressure metal-organic chemical vapour deposition on an AlN/sapphire template is reported. The influence of growth conditions on the p-type conductivity of the Al xGa 1-xN (x = 0.35) alloy was investigated. It was found that the p-type resistivity of the AlGaN alloy demonstrates a marked dependence on the Mg concentration, V/III ratio and group III element flow rate. A minimum p-type resistivity of 3.5 Ω cm for Al xGa 1-xN (x = 0.35) epilayers was achieved. A Ni/Au (10 nm/100 nm) ohmic contact was also fabricated and a specific contact resistivity of 8.1 × 10 -2 Ω cm 2 was measured. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
Open Access
On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current-voltage (I-V) and admittance spectroscopy methods
(Elsevier, 2011-06-08) Demirezen, S.; Altindal, S.; Özelik, S.; Özbay, Ekmel
In order to explain the experimental effect of interface states (N ss) and series resistance (Rs) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of (Ni/Au)/Al 0.22Ga0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/ω-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (-5 V)-(+5 V), respectively. The voltage dependent Rs profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (σac) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C m) and conductance (Gm/ω) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of Nss and R s is confirmed to have significant effect on non-ideal I-V, C-V and G/ω-V characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/ GaN heterostructures.
Open Access
Point normal metal-superconductor (NS) contact in nonballistic regime
(World Scientific Publishing, 2003) Askerzade, İ. N.; Kulik, Igor Orestovich
We analyze the point NS contact conductivity taking into account the depression of superconductivity at high-injection current density and Andreev reflection at the adaptive NS boundary. The dependence of the excess current on the voltage, as well as conductivity of contact at arbitrary voltage is obtained.