Browsing by Author "Lu, TC"

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A novel erase scheme to suppress overerasure in a scaled 2-bit nitride storage flash memory cell
(2004-09-01)
Yeh, CC
;
Wang, TH
;
Tsai, WJ
;
Lu, TC
;
Liao, YY
The cause of over-erasure in a two-bit nitride storage Flash memory cell is investigated. Extra positive charges accumulated above the n(+) unction and channel-shortening enhanced drain-induced barrier lowering effect are found to be responsible for threshold voltage (V-t) lowering in an over-erased cell. A modified erase scheme is proposed to resolve this issue. By applying a source voltage during erase, the erase speed can be well controlled for cells with different channel lengths and a wide range of program-state Vt distribution, which will reduce overerasure significantly.
A novel fully CMOS process compatible PREM for SOC applications
(2005-03-01)
Yeh, CC
;
Wang, TH
;
Tsai, WJ
;
Lu, TC
;
Liao, YY
A novel nonvolatile memory cell named programmable resistor with eraseless memory (PREM) is proposed for system on chip applications for the first time. PREM combines a novel "eraseless" algorithm and the progressive breakdown of an ultrathin oxide. No or one extra mask is needed with a standard CMOS process. Multitime programming, multilevel cell, nonvolatility, and low-voltage operation are realized. Good reliability is demonstrated based on the result of a single cell.
A novel PHINES flash memory cell with low power program/erase, small pitch, two-bits-per-cell for data storage applications
(2005-04-01)
Yeh, CC
;
Wang, TH
;
Tsai, WJ
;
Lu, TC
;
Chen, MS
A novel programming by hot-hole injection nitride electron storage (PHINES) Flash memory technology is-developed. The memory bit size of 0.046 mu m(2) is fabricated based on 0.13-mu m technology. PHINES cell uses a nitride trapping storage cell structure. Fowler-Nordheim (FN) injection is performed to raise V-t in erase while programming is done by lowering a local V-t through hand-to-hand tunneling-induced hot hole (BTBT HH) injection. Two-bits-per-cell feasibility, low-power and high-speed program/erase, good endurance and data retentivity make it a promising candidate for Flash EEPROM technology in gigabit era applications.
A novel soft-program for a narrow erased state Vt distribution, read disturbance suppression and over-program annihilation in multilevel cell flash memories
(2003-04-01)
Yeh, CC
;
Fan, TH
;
Lu, TC
;
Wang, TH
;
Pan, S
In floating gate flash memories, anode hot hole injection induced by the channel FN erase will result in tunnel oxide, degradation, severe read disturbance and an abnormally fast program. All of these issues are critical for multilevel cell (MLC) flash memory design, which requires precise threshold voltage placement, good data retentivity and programming controllability. In this paper, a novel soft-program scheme is proposed to narrow the threshold voltage distribution in the first level. Cycling-induced read disturbance and programming inaccuracy are also reduced. This technique is essential for the application of more-than-2-bit MLC, flash memories.
A parallel Poisson generator using parallel prefix
(1996-02-01)
Lu, TC
;
Hou, YS
;
Chen, RJ
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資訊工程學系
;
Department of Computer Science
In this paper, we use the renewal theory to develop a Poisson random number algorithm without restart. A parallel Poisson random number generator is designed based on this algorithm and prefix computation. This generator iteratively produces m Poisson random numbers with mean mu in average time complexity O([m mu/n]f(n, p)) on EREW PRAM, where f(n,p) is the time for computing an n-element parallel prefix on p processors in each iteration, assuming that parallel uniform random numbers can be generated at the rate of one number per unit time per processor. If n is selected near m mu, it achieves linear speedup when p is small and the average time complexity is O(log(m mu)) when p is O(m mu).
AlGaInP light-emitting diodes with stripe patterned omni-directional reflector
(2006-02-01)
Lee, YJ
;
Lu, TC
;
Kuo, HC
;
Wang, SC
;
Liou, MJ
An n-side-up AlGaInP-based light-emitting diode (LED) with a stripe-patterned omni-directional reflector (ODR) was fabricated by adopting the adhesive-layer bonding scheme. Comparing to the conventional ODR LED, the stripe-patterned ODR LED significantly enhanced the output power with an only slight higher forward voltage. This improvement was analyzed by the scanning near-field optical microscope (SNOM) and could be attributable to the geometrical shape of stripe patterns that redirects the guided light towards to the escaping cone of the LED surface. The optimized dimension of stripe patterns was also calculated by simply modeling a LED dice with a stripe-patterned ODR structure, according to optical ray-tracing method.
Aluminum incorporation into AlGaN grown by low-pressure metal organic vapor phase epitaxy
(2006-05-15)
Huang, GS
;
Yao, HH
;
Lu, TC
;
Kuo, HC
;
Wang, SC
Aluminum (Al) incorporation in AlxGa1-xN films grown by low-pressure metal organic vapor phase epitaxy using trimethylaluminum (TMAl) and trimethylgallium as group III precursors has been systematically studied. The solid phase Al composition of the AlxGa1-xN films varied nonlinearly with the Al gas phase composition. The incorporation kinetics of AlxGa1-xN alloy has been analyzed by using an adsorption-trapping model. Two parameters were used to characterize the properties of Al incorporation, i.e., the capture radius and the adsorption time of Al atoms. An exponential function of the Al composition of the AlxGa1-xN films versus the TMAl gas flow rate was obtained. It was demonstrated that the adsorption time of the Al atom was larger than the growth time of one atomic layer. The effects of ammonia flow rate, crystal growth rate, and growth temperature on the adsorption parameters were also discussed. (c) 2006 American Institute of Physics.
An endurance evaluation method for flash EEPROM
(2004-05-01)
Zous, NK
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Chen, YJ
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Chin, CY
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Tsai, WJ
;
Lu, TC
Trap generation is hard to estimate in a Flash cell due to a dynamic stress field during program and erase. In this paper, a linear correlation is found between the erase state V-T rollup, and cycling V-T window. With the knowledge of the time dependence of erase stress field based on Fowler-Nordheim (FN) tunneling, the V-T rollup during cycling is evaluated by incorporating field dependent oxide trap generation. The extracted Delta V-T degradation slope during constant FN stress can be applied quantitatively to predict the V-T window closure during Flash cell cycling.
An optically pumped blue GaN-based vertical-cavity surface emitting laser employing AIN/GaN and Ta2O5/NO2 distributed bragg reflectors
(2005)
Kao, CC
;
Yao, HH
;
Peng, YC
;
Lu, TC
;
Kuo, HC
The laser action of GaN-based VCSEL with 3-lambda cavity and hybrid DBR mirrors, consisting of AlN/GaN and Ta2O5/SiO2 DBR was achieved under the optical pumping at room temperature. The laser emits 448nm blue wavelength with a linewidth of 0.25nm above threshold.
Characteristics of monolithically integrated two-wavelength laser diodes with aluminum-free active layers
(2001-02-12)
Lu, TC
;
Fu, R
;
Shieh, HM
;
Huang, KJ
;
Wang, SC
A two-wavelength integrated laser diode (TWINLD) with aluminum-free active areas (AAA) has been realized by monolithically combining two different laser material structures in a single chip utilizing the metalorganic chemical vapor deposition growth and regrowth techniques. The single TWINLD chip comprises two ridge wave-guide lasers, one is an InGaP/InGaAlP material structure for a 650 nm red laser, and another is an InGaAsP/AlGaAs material structure with AAA for a 780 nm infrared laser. The chip geometry is 300 mum long and 300 mum wide with a separation of 150 mum between two laser emission spots. The ridge widths are 3.5 and 2 mum for the red and IR laser, respectively, and both lasers emit a single transverse mode with a threshold current of 12 mA for a 650 nm laser and 14 mA for a 780 nm laser under continuous wave operation condition. (C) 2001 American Institute of Physics.
Comparisons of InP/InGaAlAs and InAlAs/InGaAlAs distributed Bragg reflectors grown by metalorganic chemical vapor deposition
(2004-02-25)
Lu, TC
;
Tsai, JY
;
Kuo, HC
;
Wang, SC
;
光電工程學系
Long wavelength vertical cavity surface emitting lasers (VCSELs) are considered the best candidates for the low cost reliable light emitters in fiber communications. The low refractive index contrast in the conventional InP-based lattice-matched distributed Bragg reflectors (DBRs), InP/InGaAsP, impeded the development of 1.3-1.5 mum VCSELs. However, the monolithic InP-based lattice-matched DBRs are still most attractive and desirable. The InP/InGaAlAs and InAlAs/InGaAlAs DBRs with larger refractive index contrast than the conventional InP/InGaAsP DBRs have been demonstrated recently. In this report, we compare these two material systems in terms of optical and electrical properties of DBRs. We found the InP/InGaAlAs DBRs have better electrical and optical properties, while the InAlAs/InGaAlAs DBRs have much lower growth complexity. (C) 2003 Elsevier B.V. All rights reserved.
Crack-free GaN/AlN distributed Bragg reflectors incorporated with GaN/AlN superlattices grown by metalorganic chemical vapor deposition
(2006-02-06)
Huang, GS
;
Lu, TC
;
Yao, HH
;
Kuo, HC
;
Wang, SC
A crack-free GaN/AlN distributed Bragg reflector (DBR) incorporated with GaN/AlN superlattice (SL) layers was grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition. Three sets of half-wave layers consisting of 5.5 periods of GaN/AlN SL layers and GaN layer were inserted in every five pairs of the 20 pair GaN/AlN DBR structure to suppress the crack generation. The grown GaN/AlN DBRs with SL insertion layers showed no observable cracks in the structure and achieved high peak reflectivity of 97% at 399 nm with a stop band width of 14 nm. Based on the x-ray analysis, the reduction in the in-plane tensile stress in the DBR structure with insertion of SL layers could be responsible for the suppression of crack formation and achievement of high reflectivity. (c) 2006 American Institute of Physics.
Effects of different n-electrode patterns on optical characteristics of large-area p-side-down InGaN light-emitting diodes fabricated by laser lift-off
(2005-11-01)
Chu, JT
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Kao, CC
;
Huang, HW
;
Liang, WD
;
Chu, CF
Large-area p-side-down InGaN light-emitting diodes (LEDs) 1000 x 1000 mu m(2) in size have been fabricated by laser lift-off (LLO). The p-side-down LEDs with different geometric patterns of n-electrodes were fabricated to investigate electrode pattern-dependent optical characteristics. The current crowding effect was observed in the large-area p-side-down InGaN LLO-LEDs. A LED with a well-designed n-electrode pattern shows a uniform distribution of light emission and a higher output power due to uniform current spreading. The output power saturation induced by the current crowding effect was investigated. In the absence of a transparent contact layer for current spreading, the n-electrode pattern has a marked influence on the current distribution and the consequent light output power of the large-area p-side-down LEDs.
Enhanced light output in InGaN/GaN light emitting diodes with excimer laser etching surfaces
(2006-04-01)
Huang, HW
;
Chu, JT
;
Kao, CC
;
Hsueh, TH
;
Lu, TC
The InGaN/GaN light-emitting diode (LED) with a top p-GaN surface nanoroughened using Ni nanomasks and laser etching has been fabricated. The light output power of the InGaN/GaN LED with a nanoroughened top p-GaN surface is 1.55-fold that of a conventional LED. The series resistance of InGaN/GaN LED was reduced by 32% due to the increase in the contact area of the nanoroughened surface.
Enhanced light output of an InGaN/GaN light emitting diode with a nano-roughened p-GaN surface
(2005-09-01)
Huang, HW
;
Chu, JT
;
Kao, CC
;
Hseuh, TH
;
Lu, TC
This investigation describes the development of an InGaN/GaN light emitting diode (LED) with a nano-roughened top p-GaN surface using an Ni nano-mask and laser etching. The light output of the InGaN/GaN LED with a nano-roughened top p-GaN surface is 1.55 times that of a conventional LED, and the wall-plug efficiency is 68% higher at 20 mA. The series resistance of the InGaN/GaN LED was reduced by 32% by the increase in the contact area of the nano-roughened surface.
Enhancing the output power of GaN-based LEDs grown on wet-etched patterned sapphire substrates
(2006-05-01)
Lee, YJ
;
Hwang, JM
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Hsu, TC
;
Hsieh, MH
;
Jou, MJ
GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57 degrees against {001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme.
Fabrication and characteristics of GaN-based microcavity light-emitting diodes with high reflectivity AIN/GaN distributed Bragg reflectors
(2006-04-01)
Peng, YC
;
Kao, CC
;
Huang, HW
;
Chu, JT
;
Lu, TC
In this paper, we report a GaN-based microcavity light-emitting diode (MCLED) which is composed of 25 pairs of high-reflectivity GaN/AlN distributed Bragg reflector (DBR) and 6 pairs of ex-situ deposited SiO2/TiO2 dielectric mirrors. The electroluminescence peak of this structure matched well with the high reflectance area of the top and bottom DBRs, and shows a narrow emission of approximately 6.7 nm. The fabricated device also shows a more excellent performance on the stability of the emission peak wavelength while varying injection current density and operating temperature than a regular LED.
Fabrication and performance of blue GaN-based vertical-cavity surface emitting laser employing AlN/GaN and Ta2O5/SiO2 distributed Bragg reflector
(2005-08-22)
Kao, CC
;
Peng, YC
;
Yao, HH
;
Tsai, JY
;
Chang, YH
GaN-based vertical-cavity surface emitting laser with 3 lambda cavity and hybrid mirrors, consisting of the 25 pairs AlN/GaN dielectric Bragg reflector and the 8 pairs Ta2O5/SiO2, was fabricated. The laser action was achieved under the optical pumping at room temperature with a threshold pumping energy density of about 53 mJ/cm(2). The laser emits 448 nm blue wavelength with a linewidth of 0.25 nm and the laser beam has a degree of polarization of about 84%. (c) 2005 American Institute of Physics.
GaN-based LEDs with Al-deposited V-shaped sapphire facet mirror
(2006-03-01)
Lee, YJ
;
Hwang, JM
;
Hsu, TC
;
Hsieh, MH
;
Jou, MJ
A GaN-based light-emitting diodes (LEDs) with V-shaped sapphire facet reflector was fabricated using the double transferred scheme and sapphire chemical wet etching. The {1-102} R-plane V-shaped facet reflector with a 57 degrees against {0001} C-axis has the superior capability for enhancing the light extraction efficiency. The light output power of the V-shaped sapphire facet reflector LED was 1.4 times higher than that of a flat reflector LED at an injection current of 20 mA. The significant improvement is attributable to the geometrical shape of sapphire facet reflector that efficiently redirects the guided light inside the chip toward to the top escape-cone of the LED surface.
High brightness AlGaInP-based light emitting diodes by adopting the stripe-patterned omni-directional reflector
(2006-02-01)
Lee, YJ
;
Lu, TC
;
Kuo, HC
;
Wang, SC
;
Liou, MJ
An n-side-up AlGaInP-based LED operating at a wavelength of 630 nm with a stripe-patterned omni-directional reflector (ODR) was fabricated by adopting the adhesive-layer bonding scheme. It is demonstrated that the periodic and geometrical shape of the stripe-patterned array improves the light extraction efficiency by increasing the extraction of guided light. Compared to the conventional ODR LED, the stripe-patterned ODR LED significantly enhanced the output power and with only a slightly higher forward voltage. This improvement was analysed by the scanning near-field optical microscope (SNOM) and the optimized dimension of stripe patterns was also calculated on the basis of a Monte Carlo ray tracing simulation. According to the above analysis, the increase of light extraction could not only be attributed to the geometrical shape of the stripe patterns that redirect the trapped light towards the top-escaping cone of the LED surface but also to the repetitive stripe-patterned array of diffracting elements that effectively diffract the guided light outside the LED surface. Moreover, the optimized dimension of the stripe pattern is 3 mu m wide, 2 mu m deep and spaced 3 mu m apart, which coincides with experimental results.