Browsing by Author "Lee, Chi-Ling"

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Effects of strained InGaN interlayer on contact resistance between p-GaN and indium tin oxide
(2007-04-30)
Lee, Chi-Ling
;
Lee, Wei-I
;
電子物理學系
;
Department of Electrophysics
Indium tin oxide (ITO), with its transparency and strong adhesion to GaN, has been used as a replacement for Ni/Au as a contact on p-GaN. However, ITO suffers from high contact resistance on p-GaN. In this work, low contact resistance between ITO and the p-GaN layer was consistently achieved using various strained InGaN layers as the interface layers between ITO and p-GaN layer. The doping of InGaN, whether n type or p type, has a relatively weak effect on the contact resistance as long as the thickness of the InGaN layer is adequately controlled. The secondary-ion-mass spectroscopy depth profile reveals that the n-type InGaN strained contact layer was also heavily doped with Mg. Results of this study demonstrate that the piezoelectric field between InGaN and p-GaN is important in reducing the barrier height of Ohmic contact. (c) 2007 American Institute of Physics.
Extended microtunnels in GaN prepared by wet chemical etch
(2006-11-13)
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
;
Lee, Chi-Ling
;
Lee, Shih-Chang
;
Lee, Wei-I
It is demonstrated in GaN that microtunnels extended beyond hundreds of microns can be easily achieved using wet chemical etch. To obtain this result, specially designed structures of GaN layers are first grown on sapphire substrates with metal-organic chemical vapor deposition and subsequently with hydride vapor phase epitaxy techniques. The prepared samples are then chemically etched in molten KOH. With the designed structure of GaN layers, extended microtunnels with triangular cross sections are formed. The crystallographic planes of the triangular bevels belong to the {11(2) over bar 2} family. The etch rate of the tunnel can be as high as 10 mu m/min at proper etching conditions. (c) 2006 American Institute of Physics.
Formation of nitride laser cavities with cleaved facets on transferred laser diodes on GaAs substrates
(2008)
Yu, Wen-Chien
;
Ye, Shu-Mei
;
Hsiao, Feng-Ke
;
Lee, Chi-Ling
;
Lee, Wei-I
Smoothly cleaved facets with high reflectivities have been demonstrated on GaN laser diodes after the devices were transferred onto GaAs substrates. The GaN based laser diode structure was first fabricated by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates. The samples were then mounted onto thin GaAs substrates using wafer-bonding technology. Laser lift-off (LLO) technique was applied to remove the original sapphire substrate and transfer the GaN laser structure onto GaAs substrates. Since the cubic substrates have well-defined laser cavity cleavage facet, the GaN structures bonded onto the substrates also formed smooth facets after cleavage. The cleaved facets of GaN laser diodes have been characterized using atomic force microscopy (AFM) with less than 2 nm roughness. The present study demonstrated the feasibility of transferring GaN laser structures onto other more appealing substrates for formation of laser cavities.
Using planarized p-GaN layer to reduce electrostatic discharged damage in nitride-based light-emitting diode
(2007-05-01)
Lee, Chi-Ling
;
Lee, Wei-I
;
電子物理學系
;
友訊交大聯合研發中心
;
Department of Electrophysics
Electrostatic discharge damage is a serious problem on nitride-based light-emitting diodes (LEDs), due to their large lattice mismatch between III-nitride material and the sapphire substrate, which induces high-density threading dislocations. In this study, GaN/GaInN-based LEDs with various thicknesses of the low-temperature planarized p-GaN layer were fabricated. We found that when the V-shaped defects were filled by the planarized p-GaN layer, the survival rate of LEDs under human-body mode -4000 V stress increases from 23 to 93% and the survival rate under machine mode -600 V stress increases from 20 to 67%. Thus the ability to endure higher electrostatic discharge stress will be greatly improved.