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Khurelbaatar, Zagarzusem,Kang, Min-Sung,Shim, Kyu-Hwan,Yun, Hyung-Joong,Lee, Jouhan,Hong, Hyobong,Chang, Sung-Yong,Lee, Sung-Nam,Choi, Chel-Jong Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.650 No.-
<P><B>Abstract</B></P> <P>Current–voltage (<I>I–V</I>) characteristics of Au/n-type Ge Schottky barrier diodes (SBDs) with and without graphene interlayer were investigated in the temperature range of 180–340 K. For both devices, the Schottky parameters –such as the barrier height and ideality factor–showed strong temperature dependence, indicating a deviation of the <I>I–V</I> characteristics from what the thermionic emission (TE) mechanism predicts. On the basis of the TE theory along with the assumption that the barrier height takes on a Gaussian distribution, the temperature dependence of the <I>I–V</I> characteristics of the Au/n-type Ge SBDs with and without graphene interlayer was explained in terms of Schottky barrier inhomogeneity. Experimental results reveal the existence of a double Gaussian distribution of barrier height in the Au/n-type Ge SBD, whereas only a single Gaussian distribution of barrier height existed in the Au/graphene/n-type Ge SBD. Furthermore, the degree of barrier inhomogeneity of the Au/graphene/n-type Ge SBD is lower than that of the Au/n-type Ge SBD. The superiority of the Schottky barrier for the Au/graphene/n-type Ge SBD could be associated with the passivation of the Ge surface by the graphene interlayer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>I–V–T</I> characteristics of Au/graphene/n-type Ge SBD. </LI> <LI> Anomalous temperature dependence of Schottky barrier parameters of Au/graphene/n-type Ge SBD. </LI> <LI> Single Gaussian distribution of barrier height in Au/graphene/n-type Ge SBD. </LI> <LI> The graphene interlayer improves barrier homogeneity associated passivating the Ge surface. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Khurelbaatar, Z.,Shim, K.-H.,Cho, J.,Hong, H.,Reddy, V.R.,Choi, C.-J. JAPAN INSTITUTE OF METALS 2015 MATERIALS TRANSACTIONS Vol.56 No.1
<P>The temperature dependence of the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of an Au/n-type Si Schottky barrier diode (SBD) with a PEDOT:PSS interlayer was investigated. The SBD parameters, such as Schottky barrier height (Phi(B)), ideality factor (n), saturation current (I-o), doping concentration (N-D), and series resistance (R-s), were obtained as a function of temperature. The Richardson constant (A**) obtained from the In(I-o/T-2) versus 1000/T plot was much less than the theoretical value for n-Si. The mean Schottky barrier height ((Phi) over bar (bo)) and standard deviation (sigma(0)) calculated using the apparent Schottky barrier height (Phi(ap)) versus 1/2kT plot were 1.26 eV and 0.15 eV, respectively. From a fit of the modified Richardson plot of In(I-0/T-2) - (q sigma)(2)/2(kT)(2) versus 1000/T, the A** was extracted as 134 A/cm(2)K(2), which was close to the theoretical value of the n-Si. The interface state densities obtained from the Au/PEDOT:PSS/n-Si SBD decreased with increasing temperature. Furthermore, the conduction mechanism dominating the reverse-bias leakage current in Au/PEDOT:PSS/n-Si SBD was described and discussed.</P>
Temperature Dependent Current Transport Mechanism in Graphene/Germanium Schottky Barrier Diode
Khurelbaatar, Zagarzusem,Kil, Yeon-Ho,Shim, Kyu-Hwan,Cho, Hyunjin,Kim, Myung-Jong,Kim, Yong-Tae,Choi, Chel-Jong The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.1
We have investigated electrical properties of graphene/Ge Schottky barrier diode (SBD) fabricated on Ge film epitaxially grown on Si substrate. When decreasing temperature, barrier height decreased and ideality factor increased, implying their strong temperature dependency. From the conventional Richardson plot, Richardson constant was much less than the theoretical value for n-type Ge. Assuming Gaussian distribution of Schottky barrier height with mean Schottky barrier height and standard deviation, Richardson constant extracted from the modified Richardson plot was comparable to the theoretical value for n-type Ge. Thus, the abnormal temperature dependent Schottky behavior of graphene/Ge SBD could be associated with a considerable deviation from the ideal thermionic emission caused by Schottky barrier inhomogeneities.
Measuring Algorithm for Tilt Angle of Tetrahedron Balancing Based on Accelerometers
Khurelbaatar.Ts,Enkhbaatar.T,Luubaatar.B,Woonchul Ham 제어로봇시스템학회 2009 제어로봇시스템학회 합동학술대회 논문집 Vol.2009 No.12
In this paper, we propose the optimal position of the acceleration sensor in a Tetrahedron Balancing for the best performance of its tilt angle measuring functioning by using accelerometers. We also introduce the estimation algorithm under the assumption that the disturbance of the accelerometer sensor is modeled as a Gaussian normal distributed random variable. Sensitivity function is selected as a performance index for the calculating the optimal position of the sensor. From the computer simulation results, we can see that the proposed algorithm can be applicable to the real system.
Khurelbaatar, Z.,Hyung, J.-H.,Kim, G.-S.,Park, N.-W.,Shim, K.-H.,Lee, S.-K. American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.6
We demonstrate locally contacted PEDOT:PSS Schottky diodes with excellent rectifying behavior, fabricated on n-type Si substrates using a spin-coating process and a reactive-ion etching process. Electrical transport characterizations of these Schottky diodes were investigated by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. We found that these devices exhibit excellent modulation in the current with an on/off ratio of similar to 10(6). Schottky junction solar cells composed of PEDOT:PSS and n-Si structures were also examined. From the current density-voltage (J-V) measurement of a solar cell under illumination, the short circuit current (I-SC), open circuit voltage (V-OC), and conversion efficiency (eta) were similar to 19.7 mA/cm(2), similar to 578.5 mV, and similar to 6.5%, respectively. The simple and low-cost fabrication process of the PEDOT: PSS/n-Si Schottky junctions makes them a promising candidate for further high performance solar cell applications.
Khurelbaatar, Z.,Kil, Y.H.,Shim, K.H.,Cho, H.,Kim, M.J.,Lee, S.N.,Jeong, J.c.,Hong, H.,Choi, C.J. Academic Press 2016 Superlattices and microstructures Vol.91 No.-
<P>We investigated the electrical properties of chemical vapor deposition-grown monolayer graphene/n-type germanium (Ge) Schottky barrier diodes (SBD) using current-voltage (I-V) characteristics and low frequency noise measurements. The Schottky barrier parameters of graphene/n-type Ge SBDs, such as Schottky barrier height (Phi(B)), ideality factor (n), and series resistance (R-s), were extracted using the forward I-V and Cheung's methods. The Phi(B) and n extracted from the forward In(I)-V plot were found to be 0.63 eV and 1.78, respectively. In contrast, from Cheung method, the Phi(B) and n were calculated to be 0.53 eV and 1.76, respectively. Such a discrepancy between the values of Phi(B) calculated from the forward I-V and Cheung's methods indicated a deviation from the ideal thermionic emission of graphene/n-type Ge SBD associated with the voltage drop across graphene. The low frequency noise measurements performed at the frequencies in the range of 10 Hz-1 kHz showed that the graphene/n-type Ge SBD had 1/f(gamma) frequency dependence, with gamma ranging from 1.09 to 1.12, regardless of applied forward biases. Similar to forward-biased SBDs operating in the thermionic emission mode, the current noise power spectral density of graphene/n-type Ge SBD was linearly proportional to the forward current. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Zagarzusem Khurelbaatar,길연호,이훈기,양종한,강석일,김택성,심규환 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.12
We report the characterization of germanium (Ge) infrared photodiodes fabricated with a Schottkybarrier contact and a interdigitated metal-semiconductor-metal (MSM) structure with goldelectrodes on n-Ge substrates. The current-volage (I-V) characteristics were studied, and parameterssuch as the ideality factor and the barrier height of the Schottky contacts were extracted. Furthemore, we estimated the dark current and the photocurrent under illumination with = 1550nm light, and we measured the capacitance-voltage (C-V) characteristics and the dependence of theresponsivity on the bias voltage of both photodiodes at room temperature. The dark currents ofthe Schottky and the MSM photodiodes were 20.2 μA and 26.0 μA under −1 V bias and −2 Vbias, respectively. In addition, the reverse breakdown voltage was high, in excess of −30 V. TheSchottky barrier height was deduced to be 0.546 eV. A maximum responsivity of 0.27 A/W wasachieved under illumination with = 1550 nm light at a 2-V bias. A typical peak was observed ata wavelength of 1600 nm, and a high responsivity was observed in the wavelength range from 1200to 1800 nm.