Yeul-Tak Sung

A study of transparent contact to vertical GaN-based light-emitting diodes

In this study, transparent indium tin oxide (ITO) deposited by sputtering was applied to laser lift-off (LLO) GaN-based vertical light-emitting diodes (VLEDs) and the electrical and optical properties of ITO films were measured as a function of annealing conditions. The measured minimum resistivity of ITO film was about 3.78×10−4Ωcm and the measured optical transmittance at 460nm was 96.8% after the annealing process. In this condition, about 1×10−5Ωcm2 of ITO contact resistance to LLO n-GaN could be obtained. By applying the transparent ITO layer to the LLO GaN-based VLEDs, a significant decrease of the forward operating voltage from 3.3to3.8V at 20mA could be obtained.In this study, transparent indium tin oxide (ITO) deposited by sputtering was applied to laser lift-off (LLO) GaN-based vertical light-emitting diodes (VLEDs) and the electrical and optical properties of ITO films were measured as a function of annealing conditions. The measured minimum resistivity of ITO film was about 3.78×10−4Ωcm and the measured optical transmittance at 460nm was 96.8% after the annealing process. In this condition, about 1×10−5Ωcm2 of ITO contact resistance to LLO n-GaN could be obtained. By applying the transparent ITO layer to the LLO GaN-based VLEDs, a significant decrease of the forward operating voltage from 3.3to3.8V at 20mA could be obtained.

Magnetic enhanced inductively coupled plasma etching of 6H-SiC

Summary form only given, as follows. Silicon carbide(SiC) is one of the attractive semiconductor materials due to its high temperature stability and high thermal conductivity for electronic devices operating at high temperature and high power levels Due to its excellent electrical, thermal, and mechanical properties, the SiC is also used as the substrate for microelectromechanical system (MEMS) However, high rate and anisotropic plasma etching is a prerequisite for the application of SiC to these device fabrications In this study, SiC was etched using a magnetic enhanced inductively coupled plasma (MEICP) in fluorine containing gases such as NF/sub 3/, SF/sub 6/, and CF/sub 4/, and over than 2/min of high etch rate could be obtained in SF/sub 6/ based plasmas. The etch characteristics of SiC and etch selectivities over mask materials such as photoresist and metals (Al, Ni, Cu, etc) were also investigated as a function of operating pressure, inductive power, and applied dc bias voltage to the substrate, etc. The etch characteristics were investigated using an optical emission spectroscopy (OES) and quadrupole mass spectrometer (QMS) The etch profiles of patterned SiC were observed by a scanning electron microscopy (SEM).