Ho Won Jang

TL;DR: Experimental results indicate the critical role of high reflectance p-contacts as well as surface texturing in improving the light extraction efficiency of the vertical LEDs for solid-state lighting.

TL;DR: In this paper, a novel synthesis-in-place method for highly ordered vertical TiO2 nanotube films on various patterned substrates and the application of the films to chemiresistive sensors was reported.

Abstract: Electrical properties of metal contacts on laser-irradiated n-type and p-type GaN surfaces were investigated using current–voltage, capacitance–voltage, and synchrotron radiation photoemission spectroscopy. After the irradiation of a KrF excimer laser pulse (600 mJ/cm2 at 248 nm for 38 ns) onto Si-doped GaN, a nonalloyed Ti/Al metallization formed an ohmic contact with the specific contact resistivity of 1.7×10−6 Ω cm2. The laser irradiation decomposed GaN into metallic Ga and nitrogen gas. The decomposed metallic Ga reacted with oxygen in air to form a Ga oxide layer with the thickness of ∼40 A, producing a large number of N vacancies near the surface. The formation of a degenerated n-type GaN layer resulted in the low contact resistivity. For Mg-doped GaN, the laser irradiation increased the effective acceptor concentration. Simultaneously, the activation efficiency of Mg dopants was enhanced by the photon-assisted breaking of Mg–H bonds and/or the removal of hydrogen atoms in the presence of oxygen, pr...

TL;DR: In this paper, an extensive investigation in the field of optical applications of nanocomposite materials has been conducted, where an optically functional phase is embedded in a transparent, processable matrix.