Electronic states at 4,4´-N,N´-dicarbazol-biphenyl (CBP)emetal (Mg, Ag, and Au) interfaces: A joint experimental and theoretical study

Bhatt Mahesh Datt,Akahasi Baba,Takeaki Sakurai,Katsuhiro Akimoto 한국물리학회 2011 Current Applied Physics Vol.11 No.3

We used ultraviolet photoelectron spectroscopy (UPS) to study the electronic structure at the interface between organic semiconductor (CBP) and metals (Mg, Ag, and Au). Controlling the injection of charges at the interface requires a better understanding of the basic mechanism of the formation of interface states. In this context, photoelectron spectroscopy and density functional theory calculations were used to investigate the interaction of CBP with metal (111) surfaces. The position of HOMO relative to the Fermi level and the magnitude of the interface dipole were measured for each interface by UPS measurement. For CBP on Au, interface state (continuous state) was observed near the Fermi level by density functional theory calculations. However, no interface state was observed for CBP on Mg and Ag. It is suggested that the interface state plays an important role in charge transport at the interface. It was analyzed by density functional theory calculations that the interface state is formed due to interaction of CBP with metals and the position of the Fermi level varies strongly with the metal work function. The mechanism of formation of interface states and electrical properties were discussed.

A Study of the Properties of the Cu/SiOC(-H)/p-Si(100)and Cu/TaN/SiOC(-H)/p-Si(100) Interface

김창영,R. Navamathavan,Heang Seuk Lee,유영훈,우종관,최치규 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.5

Metal-insulator-semiconductor (MIS) structures based on low-dielectric-constant SiOC(-H) films with Cu (electrode) and TaN (barrier) layers are compared to study the effect of the electrode materials on the properties of the dielectric/semiconductor interface. The detailed experimental results for the C-V, G/! -V, and I-V characteristics were analyzed out in order to extract the electrical parameters, such as the interface state density, the fixed charge density, the flat band voltage, and the breakdown strength of the low- dielectric SiOC(-H) film with the stack of Cu/SiOC(-H)/p- Si(100)/Al and Cu/TaN/SiOC(-H)/p-Si(100)/Al structures. The capacitance and the conductance values were to three times higher for the 200 ˚C annealed Cu/SiOC(-H)/p-Si(100)/Al structure than they were for the as-deposited one whereas no significant change was observed with the Cu/TaN/SiOC(-H)/p-Si(100)/Al structure. The surface state density in the Cu/TaN/SiOC(-H)/p-Si(100)/Al structure was considerably lower than that in the Cu/SiOC(-H)/p-Si(100)/Al structure. Metal-insulator-semiconductor (MIS) structures based on low-dielectric-constant SiOC(-H) films with Cu (electrode) and TaN (barrier) layers are compared to study the effect of the electrode materials on the properties of the dielectric/semiconductor interface. The detailed experimental results for the C-V, G/! -V, and I-V characteristics were analyzed out in order to extract the electrical parameters, such as the interface state density, the fixed charge density, the flat band voltage, and the breakdown strength of the low- dielectric SiOC(-H) film with the stack of Cu/SiOC(-H)/p- Si(100)/Al and Cu/TaN/SiOC(-H)/p-Si(100)/Al structures. The capacitance and the conductance values were to three times higher for the 200 ˚C annealed Cu/SiOC(-H)/p-Si(100)/Al structure than they were for the as-deposited one whereas no significant change was observed with the Cu/TaN/SiOC(-H)/p-Si(100)/Al structure. The surface state density in the Cu/TaN/SiOC(-H)/p-Si(100)/Al structure was considerably lower than that in the Cu/SiOC(-H)/p-Si(100)/Al structure.

Effect of doping on metal doped semiconductor

Bhatt Mahesh Datt,Shugo Suzuki,Takeaki Sakurai,Katsuhiro Akimoto 한국물리학회 2011 Current Applied Physics Vol.11 No.2

The effect of doping on position of interface states for metal doped bathocuproine (BCP) was studied with density functional theory (DFT). The doping of Ca atoms with BCP induces the formation of interface states with shift in their relative positions from Fermi level and approximately no shift in HOMO position of BCP molecule. The shift in the position of interface states towards higher binding energy was believed to be due to the presence of doping excess electrons from Ca at the interface. The analysis of modification in intensity of LUMO or EF or interface states, suggests the formation of multiply charged anions in heavily doped film. It clearly gives the direct evidence for the origin of the doping interface states in organic molecules. The effects of Ca doping on electrical properties were discussed.

Electrical transport properties of Au/SiO2/n-GaN MIS structure in a wide temperature range

B. Prasanna Lakshmi,M. Siva Pratap Reddy,A. Ashok Kumar,V. Rajagopal Reddy 한국물리학회 2012 Current Applied Physics Vol.12 No.3

The temperature-dependent electrical properties of Au/SiO2/n-GaN metal-insulator-semiconductor (MIS)structure have been investigated in the temperature range of 120e390 K. Anomalous strong temperature dependencies of the barrier height (φbo), ideality factor (n), interface state density (NSS) and series resistance (RS) are obtained. Such behaviour is attributed to barrier inhomogeneities by assuming a Gaussian distribution of barrier heights (GD BHs) at the interface. It is evident that the diode parameters such as zero-bias barrier height increases and the ideality factor decreases with increasing temperature. The values of series resistance that are obtained from Cheung’s method is decreasing with increasing in temperature. The temperature-dependent currentevoltage characteristics of the MIS diode have been shown a double Gaussian distribution giving mean barrier heights of 0.38 eV and 1.06 eV and standard deviations of 0.0561 and 0.2742 V, respectively. A modified ln (Io/T2) - q2so 2/2k2T2 versus 103/T plot for the two temperature regions gives 4bo and A* as 0.55 eV and 11.56 A cm-2 K-2, and 1.02 eV and 23.48 A cm-2 K-2 respectively. The Interface state density values are calculated by IeV and CeV measurements at different temperatures using Terman’s method. It is observed that the interface state density decreases with increase in temperature (120e390 K). Therefore, it has been concluded that the temperature dependence of the forward IeV characteristics of the Au/SiO2/n-GaN Schottky diodes can be explained with a double GD of the BHs.

Thickness Dependence on Interfacial and Electrical Properties in Atomic Layer Deposited AlN on <i>c</i> -plane GaN

Kim, Hogyoung,Yoon, Hee Ju,Choi, Byung Joon Springer US 2018 Nanoscale research letters Vol.13 No.1

<P>The interfacial and electrical properties of atomic layer deposited AlN on n-GaN with different AlN thicknesses were investigated. According to capacitance–voltage (<I>C</I>–<I>V</I>) characteristics, the sample with a 7.4-nm-thick AlN showed the highest interface and oxide trap densities. When the AlN thickness was 0.7 nm, X-ray photoelectron spectroscopy (XPS) spectra showed the dominant peak associated with Al–O bonds, along with no clear AlN peak. The amount of remained oxygen atoms near the GaN surface was found to decrease for the thicker AlN. However, many oxygen atoms were present across the AlN layer, provided the oxygen-related defects, which eventually increased the interface state density. The barrier inhomogeneity with thermionic emission (TE) model was appropriate to explain the forward bias current for the sample with a 7.4-nm-thick AlN, which was not proper for the sample with a 0.7-nm-thick AlN. The reverse leakage currents for both the samples with 0.7- and 7.4-nm-thick AlN were explained better using Fowler–Nordheim (FN) rather than Poole–Frenkel emissions.</P>

Barrier lowering and leakage current reduction in Ni-AlGaN/GaN Schottky diodes with an oxygen-treated GaN cap layer

우현석,이종경,조용철,한재석,김종민,김형상,노정현,이준호,박정호,한철구,임현식 한국물리학회 2015 Current Applied Physics Vol.15 No.9

We report on the effect of oxygen annealing for GaN surface on the Schottky barrier configuration and leakage current in Ni-AlGaN/GaN Schottky barrier diodes. After oxygen annealing, their turn-on voltage and reverse-bias leakage current characteristics are significantly improved due to a reduction in the Schottky barrier height (SBH) and suppression in the surface states respectively. Interface state density extracted from the Terman method was reduced by 2 orders of magnitude. X-ray photoelectron spectroscopy measurements show that the oxygen annealing induces Ga2O3 on the GaN surface. The formation of Ga2O3 reduces the interface state density as well as lowers the SBH through the modification of hybridized metal induced gap states.

Barrier lowering and leakage current reduction in Ni-AlGaN/GaN Schottky diodes with an oxygen-treated GaN cap layer

Woo, H.,Lee, J.,Jo, Y.,Han, J.,Kim, J.,Kim, H.,Roh, C.H.,Lee, J.H.,Park, J.,Hahn, C.K.,Im, H. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.9

We report on the effect of oxygen annealing for GaN surface on the Schottky barrier configuration and leakage current in Ni-AlGaN/GaN Schottky barrier diodes. After oxygen annealing, their turn-on voltage and reverse-bias leakage current characteristics are significantly improved due to a reduction in the Schottky barrier height (SBH) and suppression in the surface states respectively. Interface state density extracted from the Terman method was reduced by 2 orders of magnitude. X-ray photoelectron spectroscopy measurements show that the oxygen annealing induces Ga<SUB>2</SUB>O<SUB>3</SUB> on the GaN surface. The formation of Ga<SUB>2</SUB>O<SUB>3</SUB> reduces the interface state density as well as lowers the SBH through the modification of hybridized metal induced gap states.

Electrical and frequency-dependent properties of Au/Sm2O3/n-GaN MIS junction with a high-k rare-earth Sm2O3 as interlayer

V. Manjunath,V. Rajagopal Reddy,P.R. Sekhar Reddy,V. Janardhanam,최철종 한국물리학회 2017 Current Applied Physics Vol.17 No.7

High-k rare-earth samarium oxide (Sm2O3) films are formed on n-GaN surface and analyzed its compositional properties by XPS measurements. XPS results specify that the Sm2O3 films are formed at the interface. Then, the Au/Sm2O3/n-GaN MIS junction is prepared with a Sm2O3 as insulating layer and correlated its electrical properties with the Au/n-GaN MS junction. The MIS junction shows highest barrier height ((0.81 eV (I-V)/1.0 eV (C-V)) for MIS junction than the MS junction (0.68 eV (I-V)/0.90 eV (C-V)). Excellent rectifying property is observed with lowest reverse leakage current and higher barrier height for the MIS junction than the MS junction, implying that the Sm2O3 insulating layer effectively modified the barrier height. The barrier heights determined from I-V, Cheung's, Norde and JS eV plot closely matched with each other, suggesting that these techniques are reliable and valid. The estimated interface state density of the MIS junction (1.990 1011 cm2eV1 (EC-0.82 eV)) is lower than the MS junction (9.204 1012 cm2eV1 (EC-0.70 eV)), which demonstrates that the Sm2O3 insulating layer performs an important role in lowering the interface state density. The frequency-dependent characteristics of the MS and MIS junctions are discussed in the frequency range of 10 kHz to 1 MHz and found that the determined capacitance values decrease with increasing frequency. The forward I-V characteristic of the MS and MIS junctions reveals the ohmic behavior at low voltage regions and space-chargelimited conduction at higher voltage regions. Results reveal that the reverse leakage current in the studied MS and MIS junctions is controlled by a Poole-Frenkel emission.

Double Layer (Wet/CVD SiO₂)의 Interface Trap Density에 대한 연구

이경수,최성호,최병덕 한국진공학회 2012 한국진공학회 학술발표회초록집 Vol.2012 No.2

질산산화법을 이용한 SiO₂/Si 구조의 계면결함 제거

최재영,김도연,김우병,Choi, Jaeyoung,Kim, Doyeon,Kim, Woo-Byoung 한국재료학회 2018 한국재료학회지 Vol.28 No.2

5 nm-thick $SiO_2$ layers formed by plasma-enhanced chemical vapor deposition (PECVD) are densified to improve the electrical and interface properties by using nitric acid oxidation of Si (NAOS) method at a low temperature of $121^{\circ}C$. The physical and electrical properties are clearly investigated according to NAOS times and post-metallization annealing (PMA) at $250^{\circ}C$ for 10 min in 5 vol% hydrogen atmosphere. The leakage current density is significantly decreased about three orders of magnitude from $3.110{\times}10^{-5}A/cm^2$ after NAOS 5 hours with PMA treatment, although the $SiO_2$ layers are not changed. These dramatically decreases of leakage current density are resulted from improvement of the interface properties. Concentration of suboxide species ($Si^{1+}$, $Si^{2+}$ and $Si^{3+}$) in $SiO_x$ transition layers as well as the interface state density ($D_{it}$) in $SiO_2/Si$ interface region are critically decreased about 1/3 and one order of magnitude, respectively. The decrease in leakage current density is attributed to improvement of interface properties though chemical method of NAOS with PMA treatment which can perform the oxidation and remove the OH species and dangling bond.