Browsing by Author "Wu, Cheng-Hsien"

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Analyzing Electric Field Effect by Applying an Ultra-Short Time Pulse Condition in Hafnium Oxide-Based RRAM
(2018-08-01)
Wu, Cheng-Hsien
;
Lin, Shih-Kai
;
Pan, Chih-Hung
;
Chen, Po-Hsun
;
Lin, Wen-Yan
In this letter, we determine the importance of the electrical field distribution and strength during the switching process by demonstrating different trends in the degree of reset and the reset pulse time. In general, a longer reset pulse time results in a higher reset energy; a higher reset energy leads to a higher degree of reset, which we obtainedby applying different width square waves. But quite notably, the opposite result was obtained using triangle waves, where a higher degree of reset occurred with a shorter rising time and lower reset energy. We believe that this is due to the electric field effect: if the voltage rises faster than the filament oxidation, the device can produce a larger effective electric field and a higher resistance in the reset process. To further investigate the mechanism, the procedure of the reset process was analyzed in detail, and COMSOL simulation is also carried out for confirmation.
Cathodoluminescence studies of GaAs nano-wires grown on shallow-trench-patterned Si
(2010-11-19)
Lee, Ling
;
Fan, Wen-Chung
;
Ku, Jui-Tai
;
Chang, Wen-Hao
;
Chen, Wei-Kuo
The optical properties of GaAs nano-wires grown on shallow-trench-patterned Si(001) substrates were investigated by cathodoluminescence. The results showed that when the trench width ranges from 80 to 100 nm, the emission efficiency of GaAs can be enhanced and is stronger than that of a homogeneously grown epilayer. The suppression of non-radiative centers is attributed to the trapping of both threading dislocations and planar defects at the trench sidewalls. This approach demonstrates the feasibility of growing nano-scaled GaAs-based optoelectronic devices on Si substrates.
Cathodoluminescence studies of GaAs nano-wires grown on shallow-trench-patterned Si
(2010-11-19)
Lee, Ling
;
Fan, Wen-Chung
;
Ku, Jui-Tai
;
Chang, Wen-Hao
;
Chen, Wei-Kuo
The optical properties of GaAs nano-wires grown on shallow-trench-patterned Si(001) substrates were investigated by cathodoluminescence. The results showed that when the trench width ranges from 80 to 100 nm, the emission efficiency of GaAs can be enhanced and is stronger than that of a homogeneously grown epilayer. The suppression of non-radiative centers is attributed to the trapping of both threading dislocations and planar defects at the trench sidewalls. This approach demonstrates the feasibility of growing nano-scaled GaAs-based optoelectronic devices on Si substrates.
Effect of charge quantity on conduction mechanism of high-and low-resistance states during forming process in a one-transistor-one-resistor resistance random access memory
(2017-05-01)
Wu, Cheng-Hsien
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Chang, Kuan-Chang
;
Chu, Tian-Jian
The forming process is a necessary and irreversible process to activate the resistance switching behavior in a resistance random access memory (RRAM) device. However, during the forming process, an overshoot current leads to device damage and causes inferior resistance switching characteristics; consequently, the process is considered to be a key factor in device degradation. In this paper, we find that a discontinuous conduction path can be formed by a pulse forming process such that the operation current can be reduced. We further investigate how the charge quantity during the forming process affects the carrier conduction mechanism of HRS, with all experiments and results demonstrated on onetransistor- one-resistor (1T1R) devices. (C) 2017 The Japan Society of Applied Physics
Impact of electrode thermal conductivity on high resistance state level in HfO2-based RRAM
(2020-09-23)
Lin, Shih-Kai
;
Wu, Cheng-Hsien
;
Chen, Min-Chen
;
Chang, Ting-Chang
;
Lien, Chen-Hsin
This study examines the influence of different electrode thermal conductivity on switching behavior during the reset process. Electrical analysis methods and an analysis of current conduction mechanism indicate that better thermal conductivity in the electrode will require larger input power in order to induce more active oxygen ions to take part in the reset process. More active oxygen ions result in a more oxidized switching layer, and cause the effective switching gap (d(sw)) to become larger in the reset process. The effect of the electrode thermal conductivity and input power are explained by our model and clarified by electrical analysis methods.
Improvement of defect reduction in semi-polar GaN grown on shallow-trenched Si(001) substrate
(2012)
Lee, Ling
;
Chien, Kun-Feng
;
Chou, Wu-Ching
;
Ko, Chih-Hsin
;
Wu, Cheng-Hsien
The improved design of sub-micron trenches on Si(001) substrate was demonstrated for defect suppression in semi-polar selectively-grown GaN layers. Cathodoluminescence and transmission electron microscopy measurements revealed a dramatically decreased density of threading dislocations and stacking faults near the surface of the overgrown GaN layer when the trench width ranged from 500 to 1500 nm. It was observed that defects were effectively trapped inside the trench when the ratio of trench depth to the SiO2 thickness is less than 0.66. In addition, a significant reduction of intrinsic polarization electric field was achieved for the InGaN/GaN multiple quantum well on the GaN selectively grown from the Si trenches.
Inert Pt electrode switching mechanism after controlled polarity-forming process in In2O3-based resistive random access memory
(2017-09-01)
Wu, Cheng-Hsien
;
Pan, Chih-Hung
;
Chen, Po-Hsun
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
In this study, we demonstrate a forming technique that enables us to control whether the switching layer of a Pt/In2O3/TiN device is near the Pt electrode or the TiN electrode. This means that In2O3-based resistive random access memory (RRAM) can be switched at either the active or inert electrode. The resistive switching current-voltage (I-V) curves for both electrodes exhibit stable memory windows. Through material and electrical analyses, we found that the reason for switching at the inert electrode is the oxygen-vacancy-rich characteristic of In2O3. Finally, a physical model is proposed to explain this phenomenon. (C) 2017 The Japan Society of Applied Physics
Modifying Indium-Tin-Oxide by Gas Cosputtering for Use as an Insulator in Resistive Random Access Memory
(2016-11)
Chen, Po-Hsun
;
Chang, Kuan-Chang
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Pan, Chih-Hung
In this paper, indium-tin-oxide (ITO) was used to act as both insulator and top electrode in resistive random access memory (RRAM) on identical bottom substrates. This is achieved by cosputtering an ITO target with nitride (N-2) or oxygen (O-2) gas as the insulator; then capping by an ITO electrode, such that both the rectifier and RRAM characteristics can be achieved before and after a forming process, respectively. In contrast, using pure ITO as an insulator does not exhibit RRAM behavior. To verify the rectifier and RRAM characteristics, material analyses and electrical measurements at various temperatures were conducted. Reliability tests including retention and endurance were also applied to verify the resistance switching stability. Finally, the rectifier and RRAM conduction models were proposed to examine the resistance switching behaviors. By applying the ITO material as both electrode and insulator, the resistance switching characteristic with high reliability is thus obtained.
Nitrogen Buffering Effect on Oxygen in Indium-Tin-Oxide-Capped Resistive Random Access Memory With NH3 Treatment
(2015-11-01)
Chen, Ji
;
Chang, Kuan-Chang
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Pan, Chih-Hung
In this letter, we demonstrate the differing influences of a nitrogen buffering effect in both the switching layer and the indium-tin-oxide (ITO) electrode layer of resistive random access memory (RRAM) which has undergone an NH3 treatment. The nitrogen buffering effect in the switching layer cannot counteract the electric field force, leading to similar I-V characteristics compared with the ITO/Hf:SiO2/TiN control structure RRAM. The nitrogen in the ITO electrode layer, however, works as an oxygen buffer and makes it easier for the redox reaction to occur, leading to improvements in performance, such as concentrated voltages and better endurance.
Obtaining Lower Forming Voltage and Self-Compliance Current by Using a Nitride Gas/Indium-Tin Oxide Insulator in Resistive Random Access Memory
(2016-12)
Chen, Po-Hsun
;
Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Tsai, Tsung-Ming
;
Pan, Chih-Hung
This paper investigates the characteristics of applying indium-tin oxide (ITO) with and without nitride gas (N-2) as the insulator in resistive random access memory (RRAM). After cosputtering an ITO target with N-2 as the insulator and capping the same ITO material as the top electrode, the device exhibits rectifier and resistance switching characteristics before and after the forming process, respectively. The Schottky diodelike rectifier mechanism was also verified by various temperature measurements. Furthermore, robust resistance switching at a positive forming voltage, smaller than that required during negative bias forming, can be achieved. Both positive and negative forming processes are examined with current fitting results, which show different dominant mechanisms when using positive or negative biases. All these mechanisms have also been verified by temperature effect experiments, which confirmed the dominant conduction mechanisms. This, in combination with the fact that the positive forming voltage itself is smaller than the negative forming voltage, and decreases with device scale down, provides two highly beneficial results. This good performance achieved by using ITO with N-2 suggests significant progress of RRAM and remarkable potential applications.
Optical Studies of GaAs Nanowires Grown on Trenched Si(001) Substrate by Cathodoluminescence
(2012-06-01)
Lee, Ling
;
Chien, Kun-Feng
;
Fan, Wen-Chung
;
Chou, Wu-Ching
;
Ko, Chih-Hsin
"The strains in GaAs nanowires, which were grown from 1700- to 80-nm-wide trenches on the Si(001) wafer with SiO2 masks, were investigated by cathodoluminescence. For 1700- to 500-nm-wide trenches, the in-plane tensile strain at 15 K decreases with the decreasing trench width. The strain increases abruptly when the trench width is 300 nm, and then decreases as the trench width is further decreased. The results revealed that the stress induced by the SiO2 sidewalls dominates when the width is less than the depth of the trench. This approach provides an effective technique to measure the strain of a single nanowire and helps for the demonstration of selectively-grown GaAs with a designed strain. (C) 2012 The Japan Society of Applied Physics"
Recovery of failed resistive switching random access memory devices by a low-temperature supercritical treatment
(2017-06-01)
Du, Xiaoqin
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Wu, Xiaojing
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Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Pan, Chih-Hung
The successful recovery of resistive switching random access memory (RRAM) devices that have undergone switching failure is achieved by introducing a low-temperature supercritical-fluid process that passivates the switching layer. These failed RRAM devices, which are incapable of switching between high-and low-resistance states, were treated with supercritical carbon dioxide with pure water at 120 degrees C for 1 h. After the treatment, the devices became operational again and showed excellent current-voltage (I-V) characteristics and reliability as before. On the basis of the current conduction mechanism fitting results, we propose a model to explain the phenomenon. (C) 2017 The Japan Society of Applied Physics
Reducing Forming Voltage by Applying Bipolar Incremental Step Pulse Programming in a 1T1R Structure Resistance Random Access Memory
(2018-06-01)
Zheng, Hao-Xuan
;
Chang, Ting-Chang
;
Xue, Kan-Hao
;
Su, Yu-Ting
;
Wu, Cheng-Hsien
This letter introduces a method of using bipolarity bias voltages in the forming process to effectively reduce the forming voltage of a one-transistor and one-resistance random access memory device. A bipolar incremental-step-pulse programming process is applied, and a complete operation pulse for the forming process is described. This method reduces forming voltage without any cost to the device performance, and the device maintains good reliability. The likely physical mechanism of this bipolar operation is also presented based on the measured electrical characteristics.
Solving the Scaling Issue of Increasing Forming Voltage in Resistive Random Access Memory Using High-k Spacer Structure
(2017-09-01)
Tseng, Yi-Ting
;
Chen, Po-Hsun
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Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Tsai, Tsung-Ming
In this study, the rising forming voltage issue during device cell scale-down in resistance random access memory (RRAM) is solved by introducing new high-permittivity (high-k) material as the side-wall spacer structure, unlike the normally used low-permittivity (low-k) material. Simulated electrical fields based on COMSOL Multiphysics software results suggest a RRAM device with a high-k spacer effectively confines the electric field. The effects of this confined electric field are notable, especially when the device cell is scaled down. The device fabrication process is modified to incorporate the high-k sidewall. Cross-sectional transmission electron microscopy imaging confirms the existence of SiO2 and HfO2 as the spacer structures in two different devices. Electrical measurements of forming voltages ranging from 1 to 0.16 mu m(2) are conducted to verify the effects. Statistical measurements confirm that the forming voltages of the devices with high-k material as sidewall do not increase with a reduction in device cell size. Moreover, reliability tests, including endurance and retention for the high-k sidewall device, also exhibit very stable resistance switching characteristics. As a result, the structure that is proposed successfully solves the forming voltage issues within small device cells in RRAM without any cost to device reliability.
The Effect of Humidity on Reducing Forming Voltage in Conductive-Bridge Random Access Memory With an Alloy Electrode
(2019-10-01)
Lin, Shih-Kai
;
Chen, Min-Chen
;
Chang, Ting-Chang
;
Lien, Chen-Hsin
;
Chang, Jing-Shuen
This letter investigates Au30Ag70 (alloy electrode)/SiO2/TiN conductive-bridge random access memory (CBRAM) to verify the influence of ambient conditions on forming voltage (V-F) and the location of galvanic reaction. Previous literature demonstrates that the galvanic reaction in CBRAM with an alloy electrode results in a lower V-F. In this work, a higher environmental H2O concentration results in a decrease in V-F. From this change in VF, we infer that environmental H2O concentration influences the amount of galvanic reaction. Moreover, we verify the location of the galvanic reaction by varying electrode thickness. Finally, we propose a physical model to explain our observations.