Microstructural, chemical states and electrical properties of Au/CuO/n-InP heterojunction with a cupric oxide interlayer

Balaram, N.,Rajagopal Reddy, V.,Sekhar Reddy, P.R.,Janardhanam, V.,Choi, Chel-Jong Elsevier 2018 Vacuum Vol.152 No.-

<P><B>Abstract</B></P> <P>Cupric oxide (CuO) is synthesized by simple chemical bath deposition method and deposited on n-type InP substrate using e-beam evaporation technique. First, the structural and chemical compositional analysis of CuO/n-InP are analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD and XPS results confirmed that the formation of CuO on n-type InP substrate. Then, Au/CuO/n-InP heterojunction is fabricated with a CuO interlayer and correlated its results with the Au/n-InP Schottky junction (SJ). The barrier height (Φ<SUB>b</SUB>) and ideality factor (n) are extracted through I-V and C-V methods and the respective values are 0.66 eV (I-V)/0.80 eV (C-V) and 1.24, and 0.78 eV (I-V)/0.94 eV (C-V) and 1.62 for the SJ and HJ diodes, respectively. By applying Cheung's and Norde functions, the Φ<SUB>b</SUB>, ideality factor and series resistance (R<SUB>S</SUB>) are derived for the SJ and HJ diodes. The derived interface state density (N<SUB>SS</SUB>) of HJ is lower than the SJ; results demonstrated that the CuO interlayer plays an important role in the decreased N<SUB>SS</SUB>. The Poole-Frenkel emission is the dominant current conduction mechanism in reverse bias of both SJ and HJ diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural and chemical properties of CuO films are analysed by XRD and XPS. </LI> <LI> Barrier height of Au/n-InP SJ was modified by CuO interlayer. </LI> <LI> Heterojunction has a good rectification ratio compared to the Schottky junction. </LI> <LI> The interface state density of HJ is lower as compared to the SJ. </LI> <LI> Poole-Frenkel mechanism is found to dominate in both SJ and HJs. </LI> </UL> </P>

Microstructural and electrical properties of Al/n-type Si Schottky diodes with Au-CuPc nanocomposite films as interlayer

Reddy, P.R. Sekhar,Janardhanam, V.,Jyothi, I.,Chang, Han-Soo,Lee, Sung-Nam,Lee, Myung Sun,Reddy, V. Rajagopal,Choi, Chel-Jong Elsevier 2017 Superlattices and microstructures Vol.111 No.-

<P><B>Abstract</B></P> <P>Au-CuPc nanocomposite films were prepared by simultaneous evaporation of Au and CuPc with various Au and CuPc concentrations. Microstructural analysis of Au-CuPc films revealed elongated Au cluster formation from isolated Au nanoclusters with increasing Au concentration associated with coalescence of Au clusters. Au-CuPc films with different compositions were employed as interlayer in Al/n-Si Schottky diode. Barrier height and series resistance of the Al/n-Si Schottky diode with Au-CuPc interlayer decreased with increasing Au concentration. This could be associated with the enhancement of electron tunneling between neighboring clusters due to decrease in spacing of Au clusters and formation of conducting paths through the composite material. Interface state density of the Al/n-Si Schottky diode with Au-CuPc interlayer increased with increasing Au concentration. This might be because the inclusion of metal decreases the crystallinity and crystal size of the polymer matrix accompanied by the formation of local defect sites at the places of metal nucleation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Au-CuPc nanocomposite films with varying Au and CuPc content were formed by co-evaporation. </LI> <LI> Au-CuPc nanocomposite films were employed as interlayer in Schottky diode. </LI> <LI> Elongated Au clusters were formed from isolated Au nanoclusters with increasing Au content. </LI> <LI> Au-CuPc interlayer with higher CuPc content showed higher barrier and series resistance. </LI> <LI> Electron tunneling increased due to formation of conducting paths between clusters. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Modification of Schottky Barrier Properties of Ti/p-type InP Schottky Diode by Polyaniline (PANI) Organic Interlayer

Reddy, P.R. Sekhar,Janardhanam, V.,Jyothi, I.,Yuk, Shim-Hoon,Reddy, V. Rajagopal,Jeong, Jae-Chan,Lee, Sung-Nam,Choi, Chel-Jong The Institute of Electronics and Information Engin 2016 Journal of semiconductor technology and science Vol.16 No.5

The electrical properties of Ti/p-type InP Schottky diodes with and without polyaniline (PANI) interlayer was investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements. The barrier height of Ti/p-type InP Schottky diode with PANI interlayer was higher than that of the conventional Ti/p-type InP Schottky diode, implying that the organic interlayer influenced the space-charge region of the Ti/p-type InP Schottky junction. At higher voltages, the current transport was dominated by the trap free space-charge-limited current and trap-filled space-charge-limited current in Ti/p-type InP Schottky diode without and with PANI interlayer, respectively. The domination of trap filled space-charge-limited current in Ti/p-type InP Schottky diode with PANI interlayer could be associated with the traps originated from structural defects prevailing in organic PANI interlayer.

Double Gaussian barrier distribution of permalloy (Ni_0.8Fe_0.2) Schottky contacts to n-type GaN

Janardhanam, V.,Jyothi, I.,Sekhar Reddy, P.R.,Cho, Jaehee,Cho, Jeong-Mook,Choi, Chel-Jong,Lee, Sung-Nam,Rajagopal Reddy, V. Elsevier 2018 Superlattices and microstructures Vol.120 No.-

<P><B>Abstract</B></P> <P>The temperature-dependent current-voltage (<I>I-V</I>) characteristics of permalloy (Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>) Schottky contacts to n-type GaN have been investigated. Magnetization measurements revealed the ferromagnetic behavior of Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB> film on n-type GaN. The Schottky barrier parameters, such as the barrier height and ideality factor, determined by thermionic emission depended on the measurement temperature, suggesting the presence of lateral inhomogeneity in the Schottky barrier. The experimental data modified by the thermionic emission model along with a Gaussian distribution of the barrier heights indicated the presence of a double Gaussian barrier distribution in the Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>/n-type GaN Schottky contact. The mean barrier heights and standard deviations for each Gaussian distribution were 0.84 & 1.32 eV and 0.10 & 0.17 eV over temperature range of 125–200 K and 225–400 K, respectively. The noise spectral density of the current fluctuations measured as a function of frequency (<I>f</I>) at room temperature followed a 1/<I>f</I> <SUP> <I>γ</I> </SUP> dependence with a <I>γ</I> value close to unity, irrespective of the applied forward bias. The 1/<I>f-</I>type noise was attributed to the barrier inhomogeneity existing at the Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>/n-type GaN Schottky interface as revealed from the temperature-dependent <I>I</I>–<I>V</I> characteristics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>/n-type GaN structure showed ferromagnetic behavior. </LI> <LI> <I>I</I>–<I>V</I>–<I>T</I> characteristics of permalloy (Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>)/n-GaN Schottky diodes were studied. </LI> <LI> Thermionic emission model with a Gaussian distribution of barriers indicates double barrier distribution. </LI> <LI> At 300 K, current noise spectral density against frequency (<I>f</I>) showed a 1/<I>f</I> dependence. </LI> <LI> 1/<I>f-</I>type noise was attributed to barrier inhomogeneity at the Ni<SUB>0.8</SUB>Fe<SUB>0.2</SUB>/n-type GaN Schottky interface. </LI> </UL> </P>

Modification of Schottky Barrier Properties of Ti/p-type InP Schottky Diode by Polyaniline (PANI) Organic Interlayer

P. R. Sekhar Reddy,V. Janardhanam,I. Jyothi,Shim-Hoon Yuk,V. Rajagopal Reddy,Jae-Chan Jeong,Sung-Nam Lee,Chel-Jong Choi 대한전자공학회 2016 Journal of semiconductor technology and science Vol.16 No.5

The electrical properties of Ti/p-type InP Schottky diodes with and without polyaniline (PANI) interlayer was investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements. The barrier height of Ti/p-type InP Schottky diode with PANI interlayer was higher than that of the conventional Ti/p-type InP Schottky diode, implying that the organic interlayer influenced the space-charge region of the Ti/p-type InP Schottky junction. At higher voltages, the current transport was dominated by the trap free space-charge-limited current and trap-filled space-charge-limited current in Ti/p-type InP Schottky diode without and with PANI interlayer, respectively. The domination of trap filled space-charge-limited current in Ti/p-type InP Schottky diode with PANI interlayer could be associated with the traps originated from structural defects prevailing in organic PANI interlayer.

Effect of copper phthalocyanine thickness on surface morphology, optical and electrical properties of Au/CuPc/n-Si heterojunction

Reddy, P. R. Sekhar,Janardhanam, V.,Jyothi, I.,Harsha, Cirandur Sri,Reddy, V. Rajagopal,Lee, Sung-Nam,Won, Jonghan,Choi, Chel-Jong SPRINGER-VERLAG 2018 APPLIED PHYSICS A MATERIALS SCIENCE AND PROCESSING Vol.124 No.2

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.