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Dive into the research topics where M. Siva Pratap Reddy is active.

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Featured researches published by M. Siva Pratap Reddy.


Journal of Physics D | 2013

Effect of oxygen species on the positive flat-band voltage shift in Al2O3/GaN metal–insulator–semiconductor capacitors with post-deposition annealing

Hee-Sung Kang; M. Siva Pratap Reddy; Dong-Seok Kim; Ki-Won Kim; Jong-Bong Ha; Yong Soo Lee; Hyun Chul Choi; Jung-Hee Lee

The electrical characteristics of the Al2O3/GaN metal‐insulator‐semiconductor capacitors are investigated focusing on the effect of post-deposition annealing (PDA) in O2 ambient. X-ray photoelectron spectroscopy analyses reveal that gallium oxynitride (GaOxNy) interfacial layer is formed at Al2O3/GaN interface even in non-annealed sample due to incorporation of the released oxygen from Al2O3. After PDA in O2 ambient, the GaOxNy interfacial layer becomes oxygen-rich which plays a role in increasing negative effective oxide charge at the Al2O3/GaN interface and hence positively shifting the flat band voltage (VFB) for the capacitors. (Some figures may appear in colour only in the online journal)


Optics Express | 2014

Dual detection of ultraviolet and visible lights using a DNA-CTMA/GaN photodiode with electrically different polarity

M. Siva Pratap Reddy; Bong-Joong Kim; Ja-Soon Jang

We demonstrated the dual-detectable DNA-CTMA/n-GaN photodiode (DG-PD) for ultraviolet and visible lights. Halogen and UV lamps are employed to recognize the visible and UV wavelength, respectively. The DG-PD under dark condition has a negative-bias shift of current-voltage (I-V) curves by 0.78 V compared to reference diode without DNA. However, the I-V curves move towards positive bias side by 0.75 V and 1.02 V for the halogen- and UV-exposed photodiode, respectively. These cause electrically different polarity and amount for halogen- and UV-induced photocurrents, indicating that the DNA-CTMA on n-GaN is quite effective for recognizing visible and UV lights as a dual-detectable photodiode. The formation and charge transport mechanisms are also discussed.


Electronic Materials Letters | 2014

Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures

M. Siva Pratap Reddy; Jung-Hee Lee; Ja-Soon Jang

The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage (I–V) and capacitance-voltage (C–V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.


Journal of Materials Chemistry C | 2015

High-performance light-emitting diodes using hierarchical m-plane GaN nano-prism light extractors

M. Siva Pratap Reddy; Herie Park; Se-Min Kim; Seon-Ho Jang; Ja-Soon Jang

We demonstrated high-performance GaN-based light-emitting diodes (LEDs) with hierarchical m-plane nano-prism light extractors on the n-GaN mesa sidewalls by using a tetramethylammonium hydroxide (TMAH)-based crystallographic etching technique. The crystallographic etching method leads to a chemically stable formation of hierarchical m-plane nano-prism structures as light extractors, increased p-carriers near the p-GaN surface, and the effective removal of the native oxides on the p-GaN surface. These results lead to considerable improvement of the p-ohmic contact properties between the p-GaN layer and the ITO electrode, remarkable device-performance characteristics, an improved efficiency droop, and a longer device lifetime. Based on the device-performance and the p-ohmic contact data, the hierarchical m-plane nano-prism structure acts as a multifunctional factor exhibiting high-efficiency photon-extraction, strong packaging effects, strong suppression of the leakage current along the sidewalls from the p-GaN to the n-GaN, and/or a partial release of the piezoelectric field across the quantum well region.


Journal of Materials Science: Materials in Electronics | 2017

Modified electrical properties and transport mechanism of Ti/p-InP Schottky structure with a polyvinylpyrrolidone (PVP) polymer interlayer

M. Siva Pratap Reddy; K. Sreenu; V. Rajagopal Reddy; Chinho Park

This paper reviews the electrical and transport properties of Ti/polyvinylpyrrolidone (PVP)/p-InP metal/interlayer/semiconductor (MIS) Schottky diode and compared its results with the Ti/p-InP metal/semiconductor (MS) diode. Analysis results showed that the barrier height (BH) and ideality factor of the MIS diode are found to be improved compared to the MS diode. This indicates that the effective BH is modified by the PVP interlayer since it creates physical barrier between the Ti metal and the p-InP substrate. It is noted that the evaluated BH by Cheung’s and ψS-V plots is in good concurrence with one another. Also, the series resistance of the MS and MIS diodes is estimated by Cheung’s functions. The insertion of the PVP interlayer led to a decrease of the interface state density in the Ti/p-InP MS diode. In addition, the relevant junction mechanisms are explained by feasible energy level band diagrams. The Poole–Frenkel emission is the governing conduction mechanism in the Ti/p-InP MS diode. However, at lower voltage region the Poole–Frenkel is conquered, whereas at higher voltage region the Schottky emission is occupied for the Ti/PVP/p-InP MIS diode.


Journal of Semiconductor Technology and Science | 2013

Influence of Series Resistance and Interface State Density on Electrical Characteristics of Ru/Ni/n-GaN Schottky structure

M. Siva Pratap Reddy; M. K. Kwon; Hee-Sung Kang; Dong-Seok Kim; Jung-Hee Lee; V. Rajagopal Reddy; Ja-Soon Jang

We have investigated the electrical properties of Ru/Ni/n-GaN Schottky structure using current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The barrier height (Fbo) and ideality factor (n) of Ru/Ni/n-GaN Schottky structure are found to be 0.66 eV and 1.44, respectively. The Fbo and the series resistance (RS) obtained from Cheungs method are compared with modified Nordes method, and it is seen that there is a good agreement with each other. The energy distribution of interface state density (NSS) is determined from the I-V measurements by taking into account the bias dependence of the effective barrier height. Further, the interface state density NSS as determined by Termans method is found to be 2.14´10 12 cm -2 eV -1 for the Ru/Ni/n-GaN diode. Results show that the interface state density and series resistance has a significant effect on the electrical characteristics of studied diode.


Electronic Materials Letters | 2014

Effect of substrate temperature on structural, optical and electrical properties of sputtered NiO-Ag nanocrystalline thin films

Y. Ashok Kumar Reddy; B. Ajitha; P. Sreedhara Reddy; M. Siva Pratap Reddy; Jung-Hee Lee

NiO-Ag thin films were deposited on Corning 7059 glass substrates by DC reactive magnetron sputtering technique and investigated the substrate temperature (Ts) dependent properties of NiO-Ag thin films. X-ray diffraction results showed that crystalline films can be obtained at high Ts and all films have a preferred crystal growth texture with face centered cubic (fcc) structure and was also confirmed by Raman studies. The grain size, transmittance, band gap, mobility and carrier concentrations were increased with Ts. Room temperature deposited films have an average roughness around 6.9 nm where as increment of Ts resulted in increased roughness up to 14 nm with nanocrystalline morphology. The optimum substrate temperature to obtain NiO-Ag films was found to be 200°C. It was found that with increasing the Ts, resistivity of the films was significantly decreased.


international conference on indium phosphide and related materials | 2012

Effect of temperature on series resistance determination of Au/polyvinyl alcohol/n-InP Schottky structures

M. Siva Pratap Reddy; Hee-Sung Kang; Dong-Seok Kim; Young-Woo Jo; Chul-Ho Won; Ryun-Hwi Kim; K. I. Jang; C.H. Chandrashekhar; Jung-Hee Lee; V. Rajagopal Reddy

The current-voltage (I-V) characteristics of Au/polyvinyl alcohol (PVA)/n-InP Schottky diode have been measured at temperature range 175-425 K. It is found that the series resistance (RS) values of Au/PVA/n-InP Schottky diode estimated from Cheungs and Nordes methods, are strongly temperature dependent. The values of barrier height and RS have very different especially towards to the lower temperatures. This is attributed to non-ideal I-V characteristics of the MIS structure and non-pure thermionic emission (TE) mechanism due to the low temperature effects.


Electronic Materials Letters | 2017

Fabrication and electrical characterization of Al/DNA-CTMA/p-type a-Si:H photodiode based on DNA-CTMA biomaterial

M. Siva Pratap Reddy; Peddathimula Puneetha; Young-Woong Lee; Seong-Hoon Jeong; Chinho Park

In this work, a deoxyribonucleic acid-cetyltrimethylammonium chloride (DNA-CTMA) biomaterial based p-type hydrogenated amorphous silicon (a-Si:H) photodiode (PD) is fabricated and its electrical characteristics are investigated. The Al/DNA-CTMA/p-type a-Si:H PD parameters are studied using current-voltage (I-V), capacitancevoltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) measurements. The barrier height and the ideality factor of the diode are found to be 0.78 eV and 1.9, respectively. The electrical and photoconductivity properties of the diode are analyzed by using dark I-V and transient photocurrent techniques. The C-V-f and G/ω-V-f measurements indicate that the capacitance and conductance of the diode depend on the voltage and frequency, respectively. The experimental results reveal that the decreases in capacitance and the increases in conductance with an increase in frequency can be explained on the basis of interface states (NSS). Series resistance (RS) measurements are performed on the diode and discussed here. The obtained electrical parameters confirm that the Al/DNA-CTMA/p-type a-Si:H PD can be used as an optical sensor for the development of commercial applications that are environmentally benign.


PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013 | 2013

Electrical properties of Au/n-InP and Au/PVA/n-InP Schottky structures

A. Umapathi; M. Siva Pratap Reddy; K. Ravindranatha Reddy; V. Rajagopal Reddy

We report on the electrical characteristics of Au/n-InP and Au/PVA/n-InP Schottky structures using current-voltage (I-V) and capacitance-voltage (C-V) measurements. It has been seen that the Au/PVA/n-InP Schottky structures showed a good rectifying behavior compared to the conventional Au/n-InP Schottky structure. Calculations showed that the Schottky barrier height and ideality factor of Au/n-InP Schottky structure is 0.57 eV (I-V), 0.71 eV (C-V) and 1.45, respectively. It is observed that the Schottky barrier height value increases to 0.66 eV (I-V), 0.82 eV (C-V) and ideality factor decreases to 1.32 for Au/PVA/n-InP Schottky structure. From the above observations, it is clear that the modification of interfacial potential barrier of Au/InP are achieved using a thin PVA organic interlayer.

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Jung-Hee Lee

Kyungpook National University

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V. Rajagopal Reddy

Sri Venkateswara University

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Hee-Sung Kang

Kyungpook National University

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