Browsing by Author "Lee, Cheng Chung"

Now showing 1 - 3 of 3

Effects of Inhomogeneous Gain and Loss on Nitride-Based Vertical-Cavity Surface Emitting Lasers
(2009-04-01)
Chen, Shih Wei
;
Lo, Ming Hua
;
Kao, Tsung Ting
;
Kao, Chih Chiang
;
Chu, Jung Tang
Nitride-based vertical cavity surface emitting lasers (VCSEL) with hybrid mirror has been investigated. We further measured the as-grown samples (without top dielectric distributed Bragg reflector) by p-photoluminescence, scanning near-field optical microscopy, and cathodoluminescence (CL). By different excitation power density, the experimental results indicated that the VCSEL devices have different lasing modes and spot sizes, represented inhomogeneous gain and loss distribution in the whole structure. The non-uniform emission intensity distribution including several bright spots of about 1 to 2 pm was observed for both VCSEL devices and as-grown samples, which was obtained from CL measurement, due to the effect of indium clusters and non-uniform micro-cavity resonant in InGaN multi-quantum wells (MQWs). The results show the significant influence on commercial applications such as light emitting diodes, lasers devices and so on. (C) 2009 The Japan Society of Applied Physics
Eliminating spherical aberration by gradient-indexed lenses: Geometrical derivation and manufacturing methods
(2007-11-01)
Lee, Cheng Chung
;
Hsu, Jia-Cherng
;
Lee, Chi-Hung
;
光電工程學系
;
Department of Photonics
Gradient-indexed lenses have been used to eliminate spherical aberration. The design is usually executed using numerical methods. We contribute a new way called concentric gradient-indexed lenses. This gives a new degree of freedom for gradient-indexed lenses design. Furthermore, the geometric nature of derivation makes the results analytical. By using this method, we get better insight into the problem of spherical aberration. We also suggest several manufacturing methods for gradient-indexed spherical shell materials.
Low-voltage Zn0.97Zr0.03O thin-film transistors incorporating high-k (Ba,Sr) TiO3 gate insulators deposited on BaRuO3(110) gate electrodes
(2006)
Lee, Jen Hao
;
Lin, Pang
;
Ho, Jia Chong
;
Lee, Cheng Chung
;
材料科學與工程學系
Low voltage of sol-gel-derived Zn0.97Zr0.03O thin-film transistors (TFTs) using (Ba,Sr)TiO3 (BST) gate insulators on BaRuO3(110), gate electrodes was investigated. Enhanced dielectric constants and suppressed leakage currents were observed in preferentially (110)-oriented BST synthesized on BaRuO3 electrodes. Compared to SiO2, BST gate dielectrics exhibited higher capacitance that led to a reduced operation voltage of 10 V. The superior interface trap density (D-it) of BST gate insulators in Zn0.97Zr0.03O-TFTs also brought about improved electrical characteristics such as mobility (mu(sat)), threshold voltage (V-th), and subthreshold slope (S) of 1.40 cm(2)/V s, 1.45 V, and 0.61 V/dec, respectively. (c) 2006 The Electrochemical Society.