<i>A Special Section on</i> Selected Peer-Reviewed Articles from the International Conference on Advanced Electromaterials 2011 (ICAE2011)

Kim, Sangsig,Jang, Ho Won,Lee, Jong-Heun,Baik, Jeong Min,Cheon-Lee, .,Lee, Geon-Woong,Cho, Hyung Koun,Choi, Ji-Won,Kim, Jong Kyu,Song, Myoung Hoon,Baek, Seung-Hyub,Kim, Soo-Kil,Kim, Soo Young,Park, Wo American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.5

Electrically driven lasing in light-emitting devices composed of n-ZnO and p-Si nanowires

Kim, Kwangeun,Moon, Taeho,Kim, Jeongyong,Kim, Sangsig IOP Pub 2011 Nanotechnology Vol.22 No.24

<P>Electrically driven lasing was demonstrated in light-emitting devices composed of n-ZnO and p-Si nanowires (NWs). The ZnO NWs were synthesized by thermal chemical vapor deposition and the Si NWs were formed by crystallographic wet etching of a Si wafer. The p–n heterojunction devices were constructed using the NWs by the direct transfer and dielectrophoresis methods. At an excitation current of 2 µA, the electroluminescence spectrum showed lasing behavior, and this phenomenon was explained by the ZnO-nanostructure-related cavity property. </P>

Site-selective Photoluminescence Spectroscopy of Er-implanted Wurtzite GaN under Various Annealing Condition

Kim, Sangsig,Sung, Man Young,Hong, Jinki,Lee, Moon-Sook The Korean Institute of Electrical and Electronic 2000 Transactions on Electrical and Electronic Material Vol.1 No.1

The ~1540 nm $^4$ $I_{13}$ 2/ longrightarro $w^4$ $I_{15}$ 2/ emissions of E $r^{3+}$ in Er-implanted GaN annealed at temperatures in the 400 to 100$0^{\circ}C$ range were investigated to gain a better understanding of the formation and dissociation processes of the various E $r^{3+}$ sites and the recovery of damage caused by the implantation with increasing annealing temperature ( $T_{A}$).The monotonic increase in the intensity of the broad defect photoluminescence(PL) bands with incresing $T_{A}$ proves that these are stable radiative recombination centers introduced by the implantation and annealing process. Theser centers cannot be attributed to implantation-induced damage that is removed by post-implantation annealing. Selective wavelength pumpling of PL spectra at 6K reveals the existence of at least nine different E $r^{3+}$ sites in this Er-implanted semiconductor. Most pf these E $r^{3+}$ PL centers are attributed to complexed of Er atoms with defects and impurities which are thermally activated at different $T_{A}$. Only one of the nine observed E $r^{3+}$ PL centers can be pumped by direct 4f absorption and this indicates that it is highest concentration E $r^{3+}$ center and it represents most of the optically active E $r^{3+}$ in the implanted sample. The fact that this E $r^{3+}$ center cannot be strongly pumped by above-gap light or broad band below-gap absorption indicates that it is an isolated center, i.e not complexed with defects or impurities, The 4f-pumped P: spectrum appears at annealing temperatures as low as 40$0^{\circ}C$, and although its intensity increase monotonically with increasing $T_{A}$ the wavelengths and linewidths of its characteristic peaks asre unaltered. The observation of this high quality E $r_{3+}$PL spectrum at low annealing temperatures illustrates that the crystalline structure of GaN is not rendered amorphous by the ion implantation. The increase of the PL intensities of the various E $R_{3+}$sites with increasing $T_{A}$is due to the removal of competing nonradiative channels with annealing. with annealing.annealing.

Sensitivity-tuned CO gas sensors with tailored Ga-doping in ZnO nanowires.

Kim, Kyoungwon,Lee, Deuk-Hee,Jeong, Dawoon,Debnath, Pulak Chandra,Lee, Dong-Yun,Kim, Sangsig,Lee, Sang Yeol American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.5

<P>Sensitivity-customization of zinc oxide (ZnO) nanowire (NW) gas sensors has been demonstrated by controlling Ga-doping, thereby tuning the resistance of the NWs. Both un-doped and 5 weight% Ga-doped ZnO (GZO) NWs are synthesized for the highly sensitive sensing within a narrow detection window and a less sensitive one within an expanded window, respectively. We have employed hot-walled pulsed laser deposition (HW-PLD) for the NW synthesis. With CO gas injection, the resistance reduction of NWs is detected and analyzed in a self-designed gas chamber that guarantees the precise control of gas flow and, gas concentration, as well as temperature. NW sensitivity is proportional to the sensing temperature and inversely proportional to the doping concentration resulting in widening the sensing window up to 230 times by the 5 wt.% Ga-doping.</P>

Impact ionization and tunneling operations in charge-plasma dopingless device

Kim, Minsuk,Kim, Yoonjoong,Lim, Doohyeok,Woo, Sola,Im, Kyeungmin,Cho, Jinsun,Kang, Hyungu,Kim, Sangsig Elsevier 2017 Superlattices and microstructures Vol.111 No.-

<P><B>Abstract</B></P> <P>In this paper, we present the impact ionization and tunneling operations in a newly designed dopingless device. Our proposed device functions selectively—as either a <I>p</I>-channel impact-ionization MOSFET (<I>p</I>-IMOS) or an <I>n</I>-channel tunneling field-effect transistor (<I>n</I>-TFET)—according to the bias conditions. To realize the dopingless device, the charge-plasma effect is employed to induce <I>n</I>- or <I>p</I>-type regions without any doping process, by choosing an electrode metal with an appropriate work function. The band diagrams, <I>I–V</I> characteristics, subthreshold swings (<I>SS</I>), and carrier-concentration profiles of the device under the <I>p</I>-IMOS and <I>n</I>-TFET operation modes are analyzed in our study, using a commercial device simulator. The device yields an extremely low <I>SS</I> of 0.53 mV/dec under the <I>p</I>-IMOS operation mode. It also exhibits a low off-current of approximately 10<SUP>−14</SUP> A/μm and a high <I>I</I> <SUB>ON</SUB>/<I>I</I> <SUB>OFF</SUB> of approximately 10<SUP>8</SUP>, under the <I>n</I>-TFET operation mode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A charge-plasma effect is employed to realize our newly designed dopingless device. </LI> <LI> The single dopingless device possesses both <I>p</I>-IMOS and <I>n</I>-TFET characteristics. </LI> <LI> Without any doping, the device can act similar to a conventional doped device. </LI> </UL> </P>

Steep switching characteristics of single-gated feedback field-effect transistors

Kim, Minsuk,Kim, Yoonjoong,Lim, Doohyeok,Woo, Sola,Cho, Kyoungah,Kim, Sangsig IOP Pub 2017 Nanotechnology Vol.28 No.5

<P>In this study, we propose newly designed feedback field-effect transistors that utilize the?positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, <I>I–V</I> characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec<SUP>−1</SUP>, an on/off current ratio of approximately 10<SUP>11</SUP>, and an on-current of approximately 10<SUP>−4</SUP> A at room temperature, demonstrating that the switching characteristics are superior to those?of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.</P>

Performance of ring oscillators composed of gate-all-around FETs with varying numbers of nanowire channels using TCAD simulation

Kim, Sutae,Kim, Minsuk,Woo, Sola,Kang, Hyungu,Kim, Sangsig Elsevier 2018 CURRENT APPLIED PHYSICS Vol.18 No.3

<P>In this paper, we investigate the performance of ring oscillators composed of gate-all-around (GAA) silicon nanowire (NW) field-effect transistors (FETs) with four different numbers of NW channels, for sub-10-nm logic applications. Our simulations reveal that ring oscillators with double, triple, and quadruple NW channels exhibit improvements of up to 50%, 85%, and 97%, respectively, in the oscillation frequencies (f(osc)), compared to a ring oscillator with a single NW channel, due to the large drive current, in spite of the increased intrinsic capacitance of a given device. Moreover, our work shows that the f(osc) improvement ratio of the ring oscillators becomes saturated with triple NW channels with additional load capacitances of 0.1 fF and 0.01 fF, which are similar to, or less than the intrinsic device capacitance (similar to 0.1 fF). Thus, our study provides an insight for determining the capacitive load and optimal number of NW channels, for device development and circuit design of GAA NW FETs. (C) 2017 Elsevier B.V. All rights reserved.</P>

Fatigue Behaviors of Silicon Nanowire Field-Effect Transistors on Bendable Substrate

Kim, Yoonjoong,Jeon, Youngin,Lim, Doohyeok,Kim, Sangsig American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.12

<P>In this study, we fabricated an island-structured silicon nanowire (SiNW) field-effect transistor (FET) on an Ecoflex substrate and analyzed the device reliability against the bending fatigue. A SiNW-FET was fabricated on a plastic substrate and this FET on the plastic substrate was transferred onto the Ecoflex substrate. Compared to a SiNW-FET on a plastic substrate, the SiNW-FET with the island plastic structure on the Ecoflex substrate showed the stable electrical characteristics under various bending strain. Variations less than 10% of the threshold voltage and transconductance were observed under the bending strain of 15%. Moreover, the electrical characteristics were maintained even after 2000 bending cycles.</P>

HgTe Nanocrystal-Based Thin-Film Transistors Fabricated on Glass Substrates

Kim, Hyunsuk,Kim, Dong-Won,Cho, Kyoungah,Kim, Sangsig IEEE 2007 IEEE electron device letters Vol.28 No.1

<P>HgTe nanocrystal-based thin-film transistors (TFTs) with Al<SUB>2 </SUB>O<SUB>3</SUB> top-gate dielectrics were fabricated on glass substrates using sintered HgTe nanocrystals as the channel layers. To the best of our knowledge, this is the first report on the fabrication of nanocrystal-based TFTs on glass substrates. Colloidal HgTe nanocrystal films were first formed on the glass substrates by spin-coating. The HgTe nanocrystal films were then sintered at 150 degC, leading to a dramatic increase in their conductance, compared with the as-deposited films. The TFTs fabricated in this letter exhibit the typical characteristics of p-channel transistors with a field-effect mobility of 1.04 cm<SUP>2</SUP>/Vmiddots, a threshold voltage of +0.2 V, and an on/off current ratio of 1times10<SUP>3</SUP>. These results suggest that spin-coating and sintering at a low temperature enable the simple and low-cost fabrication of nanocrystal-based TFTs on glass substrates</P>

Feedback and tunneling operations of a <i>p</i> ⁺-<i>i</i>-<i>n</i> ⁺ silicon nanowire field-effect transistor

Kim, Yoonjoong,Lim, Doohyeok,Cho, Jinsun,Kim, Sangsig IOP 2018 Nanotechnology Vol.29 No.43

<P>In this paper, we describe the feedback and tunneling operations of a dual top gate field-effect transistor (FET) with a <I>p</I> <SUP>+</SUP>-<I>i</I>-<I>n</I> <SUP>+</SUP> doped silicon nanowire channel. The transistor functions selectively in either a feedback FET (FBFET) or a tunneling FET mode by modulating the source-to-drain voltage, and it features an outstanding subthreshold swing characteristic of 6.15 mV dec<SUP>–1</SUP> with an on/off current ratio (<I>I</I> <SUB>on</SUB>/<I>I</I> <SUB>off</SUB>) of approximately 10<SUP>6</SUP> in the feedback operating mode and of 41.3 mV dec<SUP>–1</SUP> with <I>I</I> <SUB>on</SUB>/<I>I</I> <SUB>off</SUB> of ∼10<SUP>7</SUP> in the tunneling operating mode. Moreover, our device in the FBFET operation mode has memory characteristics with a retention time of 10<SUP>4</SUP> s and a program/erase endurance up to 10<SUP>3</SUP> cycles owing to the positive feedback loop in the channel region. This study demonstrates the promising potential of our devices in the development of multifunctional electronics.</P>