Rectifying and breakdown voltage enhancement of Au/n-GaN Schottky diode with Al-doped ZnO films and its structural characterization

Janardhanam, V.,Jyothi, I.,Lee, Sung-Nam,Reddy, V. Rajagopal,Choi, Chel-Jong Elsevier S.A. 2019 Thin Solid Films Vol.676 No.-

<P><B>Abstract</B></P> <P>Radio frequency magnetron sputtered Al-doped zinc oxide (AZO) thin films were formed on n-type gallium nitride (GaN). X-ray diffraction reflections and Raman modes confirmed the formation of the AZO films. The optical band gap of the deposited AZO film was found to be 3.31 eV and exhibited a fairly smooth surface and continuous growth across the surface with a grainy structure. The Au/AZO/n-GaN heterojunction Schottky diode was fabricated and investigated the influence of the presence of AZO layer in Au/n-GaN Schottky diode, characterizing its electrical and breakdown voltage properties. The AZO layer led to an excellent improvement in the rectifying behavior with an increase in barrier height of the Au/n-GaN Schottky diode from 0.69 to 0.90 eV. Reverse breakdown voltage of the Au/n-GaN Schottky diode and Au/AZO/n-GaN heterojunction diode were obtained to be 86 and 232 V, respectively, without any edge termination methods. The AZO layer effectively reduced the interface states in the Au/n-GaN Schottky diodes. Schottky and Poole-Frenkel emission mechanisms dominated the reverse current in Au/n-GaN Schottky diode and Au/AZO/n-GaN heterojunciton diode, respectively. The results signify the importance of the metal-insulator-semiconductor structure and in particular the AZO layer in reducing the leakage current and improving the device performance. A further improvement in breakdown voltage can be achieved by employing field plate and guard-ring structures for edge termination.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fabricated Au/Al-doped ZnO (AZO)/n-GaN heterojunction diode by sputtering AZO films. </LI> <LI> X-ray diffraction and Raman modes confirmed the formation of AZO films. </LI> <LI> AZO films deposited on GaN exhibited a fairly smooth surface with a grainy structure. </LI> <LI> Excellent improvement in rectification of Au/n-GaN Schottky diode by AZO insertion. </LI> <LI> Breakdown voltage of Au/n-GaN Schottky diode rises from 86 to 232 V by AZO insertion. </LI> </UL> </P>

Current–voltage and low-frequency noise analysis of heterojunction diodes with various passivation layers

Ko, Young-Uk,Yun, Ho-Jin,Jeong, Kwang-Seok,Kim, Yu-Mi,Yang, Seung-Dong,Kim, Seong-Hyeon,Kim, Jin-Sup,An, Jin-Un,Lee, Hi-Deok,Lee, Ga-Won Elsevier 2016 THIN SOLID FILMS - Vol.598 No.-

<P><B>Abstract</B></P> <P>Low-frequency noise (1/<I>f</I> noise) has been analyzed to characterize the amorphous/crystalline silicon heterojunction diodes with passivation layer of a-Si:H (p–i–n), Al<SUB>2</SUB>O<SUB>3</SUB> (p–Al<SUB>2</SUB>O<SUB>3</SUB>–n), and ZnO (p–ZnO–n) and without passivation (p–n). Four types of diodes show high ideality factors and the dependence of the reverse leakage current on the electric field shows that the diodes commonly follow the Poole–Frenkel model, which is field-assisted thermionic emission from the traps in the materials. However, the conduction mechanism in the reverse bias can be more easily clarified from the bias dependence of the 1/<I>f</I> noise. That is, the p–i–n and p–n diodes are affected by the diffusion current mechanism, and the p–Al<SUB>2</SUB>O<SUB>3</SUB>–n and p–ZnO–n diodes with an inferior interface are affected by the generation–recombination current mechanism. This indicates that the p–i–n and p–n diodes have a better interface quality than the p–Al<SUB>2</SUB>O<SUB>3</SUB>–n and the p–ZnO–n. These results show that the 1/<I>f</I> noise measurement can be a useful and more sensitive method to estimate the interface quality of heterojunction diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Leakage current is on Poole–Frenkel in heterojunction diode with inferior interface. </LI> <LI> Low-frequency noise is proposed to evaluate heterojunction diode. </LI> <LI> Low-frequency noise is useful to distinguish the leakage conduction mechanism. </LI> </UL> </P>

Fabrication of the heterojunction diode from Y-doped ZnO thin films on p-Si substrates by sol-gel method

Sharma, Sanjeev K.,Singh, Satendra Pal,Kim, Deuk Young Elsevier 2018 Solid state communications Vol.270 No.-

<P><B>Abstract</B></P> <P>The heterojunction diode of yttrium-doped ZnO (YZO) thin films was fabricated on p-Si(100) substrates by sol-gel method. The post-annealing process was performed at 600 °C in vacuum for a short time (3 min) to prevent inter-diffusion of Zn, Y, and Si atoms. X-ray diffraction (XRD) pattern of as-grown and annealed (600 °C in vacuum) films showed the preferred orientation along the c-axis (002) regardless of dopant concentrations. The uniform surface microstructure and the absence of other metal/oxide peaks in XRD pattern confirmed the excellence of films. The increasing bandgap and carrier concentration of YZO thin films were interpreted by the BM shift, that is, the Fermi level moves towards the conduction band edge. The current-voltage characteristics of the heterojunction diode, In/n-ZnO/p-Si/Al, showed a rectification behavior. The turn-on voltage and ideality factor of n-ZnO/p-Si and n-YZO/p-Si were observed to be 3.47 V, 2.61 V, and 1.97, 1.89, respectively. Y-dopant in ZnO thin films provided more donor electrons caused the shifting of Fermi-energy level towards the conduction band and strengthen the interest for heterojunction diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heterojunction diode of Y-doped ZnO thin film/p-Si (100) fabricated by sol gel method. </LI> <LI> Post-annealing at 600 °C in vacuum for 3 min to prevent inter-diffusion of Zn, Y, and Si atoms. </LI> <LI> I-V of <I>In/n-ZnO/p-Si/Al</I>, showed a rectification behavior. </LI> <LI> Turn-on voltage/Ideality factor of n-ZnO/p-Si & n-YZO/p-Si were decreased to be 3.47 V, 2.61 V, and 1.97, 1.89. </LI> <LI> Y-concentration provided more donor caused the shifting of Fermi-energy level towards the conduction band and strengthen the interest for heterojunction diodes. </LI> </UL> </P>

"후열처리 분위기에 따른 깊은 준위결함의 변화가 Ga2O3/SiC 이종접합 다이오드에 미치는 영향 분석"

정승환,신명철,Mathieu Jarry,구상모 한국전기전자학회 2024 전기전자학회논문지 Vol.28 No.1

"본 연구에서는 다양한 가스 분위기에서 후열처리를 진행한 후 Ga2O3/SiC 이종접합 다이오드의 깊은 준위 결함 변화를 Deep Level Transient Spectroscopy(DLTS) 기법으로 분석하여 깊은 준위 결함의 변화가 Ga2O3/SiC 이종접합 소자의 전기적 특성에미치는 영향을 조사하였다. 또한, J-V 측정 및 Hall 측정을 통한 전기적 특성 분석을 실시하였고, N2 분위기에서 열처리된 소자에서3.06 × 10-2 A/cm2로 가장 높은 on-state current가 측정되었으며, carrier concentration은 3.8 × 1014 cm-3로 증가하는것이 관측되었다. 이는 후열처리 분위기에 따른 깊은 준위 결함의 변화가 전기적 특성에 영향을 미칠 수 있음을 시사한다." "In this research, we explored the influence of post-annealing atmospheres on the electrical properties of Ga2O3/SiC heterojunction diodes. We fabricated Ga2O3/SiC heterojunction diodes by RF sputtering and after the fabrication the post-annealing in various gas atmospheres was performed. We measured the changes in deep-level defects using Deep Level Transient Spectroscopy (DLTS) and we conducted an electrical characteristic of J-V measurement and Hall measurement to analyzed the effects of annealing atmosphere on Ga2O3/SiC heterojunction diode. In the N2 annealed devices, the highest on-state current was measured as 3.06 × 10-2 A/cm^2, and an increase in carrier concentration of 3.8 × 1014 cm-3 was observed. This confirms that the variations in deep level defects due to the post-annealing atmosphere can influence the electrical properties."

Modulation of Quantum Tunneling <i>via</i> a Vertical Two-Dimensional Black Phosphorus and Molybdenum Disulfide p–n Junction

Liu, Xiaochi,Qu, Deshun,Li, Hua-Min,Moon, Inyong,Ahmed, Faisal,Kim, Changsik,Lee, Myeongjin,Choi, Yongsuk,Cho, Jeong Ho,Hone, James C.,Yoo, Won Jong American Chemical Society 2017 ACS NANO Vol.11 No.9

<P>Diverse diode characteristics were observed in two (2D) black phosphorus (BP) and molybdenum disulfide (MoS2) heterojunctions. The characteristics of a backward rectifying diode, a Zener diode, and a forward rectifying diode were obtained from the heterojunction through-thickness modulation of the BP flake or back gate modulation. Moreover, a tunnel diode with a precursor to negative differential resistance can be realized by applying dual gating with a sad polymer electrolyte layer as a top gate dielectric material. Interestingly, a steep subthreshold swing Of 55 mV/dec was achieved in a top-gated 2D BP-MoS2 junction. Our simple device architecture and chemical doping-free processing guaranteed the device quality. This work helps us understand the fundamentals of tunneling in 2D semiconductor heterostructures and shows great potential in future applications in integrated low-power circuits.</P>

Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode

Sharma, S.K.,Heo, S.,Lee, B.,Lee, H.,Kim, C.,Kim, D.Y. Elsevier 2014 Current Applied Physics Vol.14 No.12

We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 <SUP>o</SUP>C) by RF sputtering. The films were subsequently annealed at 700 <SUP>o</SUP>C in N<SUB>2</SUB> ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current-voltage (I-V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 <SUP>o</SUP>C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.

Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode

샤르마,허성은,이병호,이황호,김창민,김득영 한국물리학회 2014 Current Applied Physics Vol.14 No.12

We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 C) by RF sputtering. The films were subsequently annealed at 700 C in N2 ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Currentevoltage (IeV) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.

버퍼막 두께에 따른 ZnO/ZnO/p-Si(111) 이종접합 다이오드 특성 평가

허주회,류혁현,이종훈,Heo, Joo-Hoe,Ryu, Hyuk-Hyun,Lee, Jong-Hoon 한국재료학회 2011 한국재료학회지 Vol.21 No.1

In this study, the effects of an annealed buffer layer with different thickness on heterojunction diodes based on the ZnO/ZnO/p-Si(111) systems were reported. The effects of an annealed buffer layer with different thickness on the structural, optical, and electrical properties of zinc oxide (ZnO) films on p-Si(111) were also studied. Before zinc oxide (ZnO) deposition, different thicknesses of ZnO buffer layer, 10 nm, 30 nm, 50 nm and 70 nm, were grown on p-Si(111) substrates using a radio-frequency sputtering system; samples were subsequently annealed at $700^{\circ}C$ for 10 minutes in $N_2$ in a horizontal thermal furnace. Zinc oxide (ZnO) films with a width of 280nm were also deposited using a radio-frequency sputtering system on the annealed ZnO/p-Si (111) substrates at room temperature; samples were subsequently annealed at $700^{\circ}C$ for 30 minutes in $N_2$. In this experiment, the structural and optical properties of ZnO thin films were studied by XRD (X-ray diffraction), and room temperature PL (photoluminescence) measurements, respectively. Current-voltage (I-V) characteristics were measured with a semiconductor parameter analyzer. The thermal tensile stress was found to decrease with increasing buffer layer thickness. Among the ZnO/ZnO/p-Si(111) diodes fabricated in this study, the sample that was formed with the condition of a 50 nm thick ZnO buffer layer showed a strong c-axis preferred orientation and I-V characteristics suitable for a heterojunction diode.

Temperature-dependent electronic charge transport characteristics at MoS₂/p-type Ge heterojunctions

Son, Seung Bae,Kim, Yonghun,Cho, Byungjin,Choi, Chel-Jong,Hong, Woong-Ki Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.757 No.-

<P><B>Abstract</B></P> <P>Significant effort has been devoted to constructing two-dimensional transition metal dichalcogenides-based hybrid heterojunctions with enhanced performance or unique functionalities for versatile device applications in emerging electronics and optoelectronics. In this study, we report the temperature-dependent electronic charge transport characteristics in MoS<SUB>2</SUB>/p-type Ge heterojunction diodes. From the current-voltage (<I>I-V</I>) characteristics of the heterojunction device, it is observed that different transport phenomena can occur depending upon the temperature and bias voltage. The charge transport is dominated by thermionic emission in the high-temperature regime above 300 K, whereas in low-temperature regime below 300 K, the charge transport mechanism transitions from the thermionic emission to the tunneling mechanism associated with trap sites. In particular, the <I>I-V</I> characteristics in the low-temperature regime show a transition from the direct tunneling at a low bias to the Fowler-Nordheim tunneling mechanism at a high bias. This could be well described by the electrical analyses on temperature-dependent <I>I-V</I> behavior and corresponding energy band diagrams.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fabrication of heterojunctions by stacking n-type MoS<SUB>2</SUB> film on a p-type Ge epilayer. </LI> <LI> Temperature-dependent current-voltage characteristics of the MoS<SUB>2</SUB>/p-type Ge device. </LI> <LI> The charge transport mechanism in three regimes. </LI> <LI> The thermionic emission is dominant in the high-temperature regime. </LI> <LI> The trap-assisted tunneling mechanism is dominant in the low-temperature regime. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis and characterization of indenofluorene-based copolymers containing 2,5-bis(2-thienyl)-N-arylpyrrole for bulk heterojunction solar cells and polymer light-emitting diodes

Tamilavan, Vellaiappillai,Sakthivel, Pachagounder,Li, Yinan,Song, Myungkwan,Kim, Chul-Hyun,Jin, Sung-Ho,Hyun, Myung Ho Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.14

<P>Two novel alternating π-conjugated copolymers, poly[2,8-(6,6′,12,12′-tetraoctyl-6,12-dihydroindeno-[1,2b]fluorene- alt-5(1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole) (P1) and poly[2,8-(6,6′,12,12′-tetraoctyl-6,12-dihydroindeno-[1,2b]fluorene- alt-5(1-(p-octylphenyl)-2,5-di(2-thienyl)pyrrole) (P2), were synthesized via the Suzuki coupling method and their optoelectronic properties were investigated. The resulting polymers P1 and P2 were completely soluble in various common organic solvents and their weight-average molecular weights (M<SUB>w</SUB>) were 5.66 × 10<SUP>4</SUP> (polydispersity: 1.97) and 2.13× 10<SUP>4</SUP> (polydispersity: 1.54), respectively. Bulk heterojunction (BHJ) solar cells were fabricated in ITO/PEDOT:PSS/polymer:PC<SUB>70</SUB>BM(1:5)/TiO<SUB>x</SUB>/Al configurations. The BHJ solar cell with P1:PC<SUB>70</SUB>BM (1:5) has a power conversion efficiency (PCE) of 1.12% (J<SUB>sc</SUB>= 3.39 mA/cm<SUP>2</SUP>, V<SUB>oc</SUB>= 0.67 V, FF = 49.31%), measured using AM 1.5 G solar simulator at 100 mW/cm<SUP>2</SUP> light illumination. We fabricated polymer light-emitting diodes (PLEDs) in ITO/PEDOT:PSS/emitting polymer:polyethylene glycol (PEG)/Ba/Al configurations. The electroluminescence (EL) maxima of the fabricated PLEDs varied from 526 nm to 556 nm depending on the ratio of the polymer to PEG. The turn-on voltages of the PLEDs were in the range of 3–8 V depending on the ratio of the polymer to PEG, and the maximum brightness and luminance efficiency were 2103 cd/m<SUP>2</SUP> and 0.37 cd/A at 12 V, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3169–3177, 2010</P> <B>Graphic Abstract</B> <P>Two novel indenofluorene-based copolymers containing 2,5-bis(2-thienyl)-N-(4-octylphenyl)pyrrole or 2,5-bis(2-thienyl)-N-(2,6-diisopropylphenyl)pyrrole were prepared for bulk hetrojunction solar cells and polymer light-emitting diodes. <img src='wiley_img_2010/0887624X-2010-48-14-POLA24101-gra001.gif' alt='wiley_img_2010/0887624X-2010-48-14-POLA24101-gra001'> </P>