Browsing by Author "Lin, H. Y."

Now showing 1 - 4 of 4

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate
(2012-03-01)
Lin, H. Y.
;
Chen, Y. J.
;
Chang, C. L.
;
Li, X. F.
;
Kuo, C. H.
Chemical wet etching on c-plane sapphire wafers by three etching solutions (H3PO4, H2SO4, and H3PO4/H2SO4 mixing solution) was studied. Among these etching agents, the mixing H3PO4/H2SO4 solution has the fastest etching rate (1.5 mu m/min). Interestingly, we found that H2SO4 does not etch the c-plane sapphire wafer in thickness; instead, a facet pyramidal pattern is formed on the c-plane sapphire wafer. GaN light-emitting diode (LED) epitaxial structure was grown on the sapphire wafer with the pyramidal pattern and the standard flat sapphire wafer. X-ray diffraction and photoluminescence measurement show that the pyramidal pattern on the sapphire wafer improved crystalline quality but augmented the compressive stress level in the GaN LED epilayer. The horizontal LED chips fabricated on the pyramidal-patterned sapphire wafer have a larger light output than the horizontal LED chips fabricated on the standard flat sapphire wafer by 20%.
Investigation of Data Pattern Effects on Nitride Charge Lateral Migration in a Charge Trap Flash Memory by Using a Random Telegraph Signal Method
(2018-01-01)
Liu, Y. H.
;
Lin, H. Y.
;
Jiang, C. M.
;
Wang, Tahui
;
Tsai, W. J.
Data pattern effects on nitride charge lateral migration and V-t retention loss in a charge trap flash memory is investigated. We use channel hot electron program and band-to-band tunneling hot hole erase to inject different amounts of electrons and holes at the two sides of a channel in a SONOS cell. An interface oxide trap near an injected charge packet and its associated random telegraph signal (RTS) are used as an internal probe to detect a local channel potential change resulting from trapped charge lateral migration. Vt retention loss and RTS in various charge storage patterns are characterized and analyzed. At a similar built-in electric field, nitride trapped holes are found to be more mobile than trapped electrons in lateral migration.
Optical characteristics of silver film on the moth-eye structure
(2007-10-01)
Ting, C. J.
;
Tsai, H. Y.
;
Chou, C. P.
;
Lin, H. Y.
;
Wu, T. C.
The development of coating optics to lower the reflected light and thereby to increase the optical efficiency of an optical system has been a very important issue for many years. Conventional solutions to this, such as multilayered alternation of high and low refractive index layers, often lead to an expensive coating process. Recently, the use of antireflection structured (ARS) surface, which is called "moth-eye structure", has been proposed as an applicable option based on both the theoretical and experimental studies. In the current study, the experimental results of the reflectance and transmittance of two different thicknesses of silver films deposited on the moth-eye structure were carried out. The moth-eye structure arrays were fabricated by holographic exposure and photolithographic processes on the polymer film. The structure arrays were consisted of periodic length of about 300 nm, with the diameter of about 250 nm and the height of 150 nm. Compared with the silver coating film on the flat PET substrate, the optical property of the silver coating film on the moth-eye structure showed a better result for the anti-reflection application. The 25 nm-thick silver film on the moth-eye structure is suggested to be applied for the car window glass of antireflective films to obtain the high performance of heat insulation with acceptable transparency in the visible range.
The performance of an acoustic levitator
(2020-01-01)
Hsu, C. H.
;
Lin, H. Y.
;
Agarwal, A.
;
Davis, I.
;
Nolan, K. P.
An acoustic levitator uses an array of ultrasonic transducers to generate a standing acoustic pressure field which exerts a radiation force on small particles, allowing the particles to be trapped, relocated, separated or combined. Experiments on levitating particles of different densities and calculations of the acoustic radiation force and moment have been reported in the literature. However, direct inspection on the acoustic pressure field pattern is seldom carried out. This paper reports an investigation on the performance of an existing acoustic levitator design, which uses off-the-shelf components, by comparing the visualized pressure field from Schlieren imaging to analytical simulations. The ability to compare Schlieren imaging results to analytical simulations readily can prove to be a vital tool. Since the simulations provide an ideal pressure field, the imaging of the levitator pressure field can highlight discrepancies between the real and ideal cases. This can be especially useful as a diagnostic tool to identify the cause of a drop in performance of the acoustic levitator in a real world scenario.