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Kim, Hogyoung,Kim, Min Kyung,Kim, Yeon Jin Materials Research Society of Korea 2016 한국재료학회지 Vol.26 No.10
Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, the electrical properties of Au and Cu Schottky contacts to n-Ge were comparatively investigated. Lower values of barrier height, ideality factor and series resistance were obtained for the Au contact as compared to the Cu contact. The values of capacitance showed strong dependence on the bias voltage and the frequency. The presence of an inversion layer at the interface might reduce the intercept voltage at the voltage axis, lowering the barrier height for C-V measurements, especially at lower frequencies. In addition, a higher interface state density was observed for the Au contact. The generation of sputter deposition-induced defects might occur more severely for the Au contact; these defects affected both the I-V and C-V characteristics.
Forward Current Transport Mechanism of Cu Schottky Barrier Formed on n-type Ge Wafer
Kim, Se Hyun,Jung, Chan Yeong,Kim, Hogyoung,Cho, Yunae,Kim, Dong-Wook The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.3
We fabricated the Cu Schottky contact on an n-type Ge wafer and investigated the forward bias current-voltage (I-V) characteristics in the temperature range of 100~300 K. The zero bias barrier height and ideality factor were determined based on the thermionic emission (TE) model. The barrier height increased and the ideality factor decreased with increasing temperature. Such temperature dependence of the barrier height and the ideality factor was associated with spatially inhomogeneous Schottky barriers. A notable deviation from the theoretical Richardson constant (140.0 Acm<sup>-2</sup>K<sup>-2</sup> for n-Ge) on the conventional Richardson plot was alleviated by using the modified Richardson plot, which yielded the Richardson constant of 392.5 Acm<sup>-2</sup>K<sup>-2</sup>. Finally, we applied the theory of space-charge-limitedcurrent (SCLC) transport to the high forward bias region to find the density of localized defect states (N<sub>t</sub>), which was determined to be 1.46 × 10<sup>12</sup> eV<sup>-1</sup>cm<sup>-3</sup>.
Kim, Hogyoung The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.5
We prepared silver Schottky contacts to O-polar and nonpolar m-plane bulk ZnO wafers. Then, by considering various transport models, we performed a comparative analysis of the current transport properties of Ag/bulk ZnO Schottky diodes, which were measured at 300, 200, and 100 K. The fitting of the forward bias current-voltage (I-V) characteristics revealed that the tunneling current is dominant as the transport component in both the samples. Compared to thermionic emission (TE), a stronger contribution of tunneling current was observed at low temperature. The reverse bias I-V characteristics were well fitted with the thermionic field emission (TFE) in both the samples. The presence of acceptor-like adsorbates, such as O<sub>2</sub> and H<sub>2</sub>O, modulated the surface conductive state of ZnO, thereby affecting the tunneling effect. The degree of activation/passivation of acceptor-like adsorbates might be different in both the samples owing to their different surface morphologies and surface defects (e.g., oxygen vacancies).
Characterization of Conduction Mechanism in Cu Schottky Contacts to p-type Ge
Kim, Se Hyun,Jung, Chan Yeong,Kim, Hogyoung The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.6
Germanium (Ge) is a promising material for next generation nanoelectronics and multiple junction solar cells. This work investigated the electrical properties in Cu/p-type Ge Schottky diodes, using current-voltage (I-V) measurements. The Schottky barrier heights were 0.66, 0.59, and 0.70 eV from the forward ln(I)-V, Cheung, and Norde methods, respectively. The ideality factors were 1.92 and 1.78 from the forward ln(I)-V method and Cheung method, respectively. Such high ideality factor could be associated with the presence of an interfacial layer and interface states at the Cu/p-Ge interface. The reverse-biased current transport was dominated by the Poole-Frenkel emission rather than the Schottky emission.
Capacitance-Voltage (C-V) Characteristics of Cu/n-type InP Schottky Diodes
Kim, Hogyoung The Korean Institute of Electrical and Electronic 2016 Transactions on Electrical and Electronic Material Vol.17 No.5
Using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements, the electrical properties of Cu/n-InP Schottky diodes were investigated. The values of C and G/ω were found to decrease with increasing frequency. The presence of interface states might cause excess capacitance, leading to frequency dispersion. The negative capacitance was observed under a forward bias voltage, which may be due to contact injection, interface states or minority-carrier injection. The barrier heights from C-V measurements were found to depend on the frequency. In particular, the barrier height at 200 kHz was found to be 0.65 eV, which was similar to the flat band barrier height of 0.66 eV.
Effect of antireflection facet coatings on the characteristics of a high-power red laser diode
Kim, Chang Zoo,Choi, Je Hyuk,Shin, Chan Soo,Kim, Hogyoung Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10
We investigated the effect of antireflection (AR) coatings on the performance of high-power red laser diodes (LDs). The AR coating at the front facet and the high reflection (HR) coating at the rear facet were deposited on cleaved facets. As an AR coating, SiO2 or Si3N4 single layers with different thicknesses were employed. When the reflectivity of the AR coating was 25%, the best LD performance was obtained. The fitting to the threshold current density vs. effective optical length plot produced a transparent current density of 310 A/cm(2). Under continuous wave (cw) operation at 15 A degrees C, the operating current was 1.41 A, and the operating voltage was 2.33 V with an optical output of 280 mW. At an operating temperature of 0 A degrees C, we observed the maximum output power of about 390 mW.
Contact Area-Dependent Electron Transport in Au/n-type Ge Schottky Junction
Kim, Hogyoung,Lee, Da Hye,Myung, Hye Seon Materials Research Society of Korea 2016 한국재료학회지 Vol.26 No.8
The electrical properties of Au/n-type Ge Schottky contacts with different contact areas were investigated using current-voltage (I-V) measurements. Analyses of the reverse bias current characteristics showed that the Poole-Frenkel effect became strong with decreasing contact area. The contribution of the perimeter current density to the total current density was found to increase with increasing reverse bias voltage. Fitting of the forward bias I-V characteristics by considering various transport models revealed that the tunneling current is dominant in the low forward bias region. The contributions of both the thermionic emission (TE) and the generation-recombination (GR) currents to the total current were similar regardless of the contact area, indicating that these currents mainly flow through the bulk region. In contrast, the contribution of the tunneling current to the total current increased with decreasing contact area. The largest $E_{00}$ value (related to tunneling probability) for the smallest contact area was associated with higher tunneling effect.
Analysis of Current Transport Properties in Nonpolar a-plane ZnO-based Schottky Diodes
Hogyoung Kim,김해리,김동욱 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.5
Using current–voltage (I–V ) measurements, we investigated the temperature-dependent transportproperties in Ag/nonpolar a-plane ZnO Schottky diodes. The bias-dependent ideality factorswere altered by the different temperatures and showed a hump at lower temperatures. The seriesresistance of the diode depended on the temperatures, which was related to the number of freecarriers contributing to the series resistance. For high forward bias, the slope m obtained from thelnI–lnV curves decreased with increasing temperature, assuring the space-charge-limited-current(SCLC) model controlled by an exponential distribution of traps. The reverse-biased current transportwas associated with the Schottky effect, with a thermally-assisted tunneling for lower voltagesand the Poole–Frenkel effect for higher voltages. The density of localized states (Nt) was obtainedby applying the theory of SCLC transport, which yielded a Nt value of 8.32 × 1011 eV−1cm−3.
Kim Hogyoung,Jung Myeong Jun,Choi Byung Joon 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.3
The Pt/Ge Schottky junctions were fabricated with an atomic layer deposition (ALD)-grown ZnO interlayer (IL) and the interfacial properties of Pt/ZnO/Ge Schottky junctions were characterized. The forward current characteristics showed that the barrier height for Pt/ZnO/Ge junction was higher than that for the Pt/Ge junction, associated with the improved interfacial quality. The thermionic feld emission model was a suitable transport mechanism for the reverse current characteristics for Pt/ZnO/Ge junction. High reverse current values for Pt/Ge junction would be due to the positive fxed charges and/or donorlike surface states. Higher barrier height and lower reverse leakage current indicate better Schottky diode characteristics for the Pt/ZnO/Ge junction. It could be inferred from the results that ALD-grown ZnO IL improved the interfacial quality of Pt/Ge Schottky junction.