Kyu Ha Baek

Improvement of light out-coupling efficiency in organic light-emitting diodes with variable nanopatterns

We present a viable method to enhance the current efficiency of organic light-emitting diodes (OLEDs) by imprinting cylindrical nanopatterns (NPs) onto a glass substrate. Herein, OLEDs equipped with an optimum NP array having a diameter of 300 nm and a periodic distance of 500 nm show a 33.4% improvement in current efficiency compared with a device without NPs. The light extraction efficiency of OLEDs was enhanced using a nanopatterned glass substrate, without any electrical degradation owing to the formation of NPs on opposite sides of the organic layers. In addition, top-emitting OLEDs can be fabricated easily by patterning the encapsulation glass.

Rapid curing of solution-processed zinc oxide films by pulse-light annealing for thin-film transistor applications

In this study, a pulse-light annealing method is proposed for the rapid fabrication of solution-processed zinc oxide (ZnO) thinfilm transistors (TFTs). Transistors that were fabricated by the pulse-light annealing method, with the annealing being carried out at 90℃ for 15 s, exhibited a mobility of 0.05 cm2/Vs and an on/off current ratio of 106. Such electrical properties are quite close to those of devices that are thermally annealed at 165℃ for 40 min. X-ray photoelectron spectroscopy analysis of ZnO films showed that the activation energy required to form a Zn-O bond is entirely supplied within 15 s of pulse-light exposure. We conclude that the pulse-light annealing method is viable for rapidly curing solution-processable oxide semiconductors for TFT applications.

Reliability investigation of ultrathin oxides grown by high pressure oxidation and nitrided in N/sub 2/O for ULSI device applications

The reliability of new ultrathin oxides grown by high pressure oxidation (HIPOX) has been evaluated in order to use gate insulators for ULSI MOSFETs. From the results of the TDDB characteristics of 75 /spl Aring/ thick HIPOX oxide nitrided at 1100/spl deg/C for 30 sec, the lifetime of the nitrided-HIPOX oxide at negative constant current stress, -1.0/spl times/10/sup -6/ A/cm/sup 2/ is about 1.2/spl times/10/sup 9/ sec. Initially, the midgap interface trap density (D/sub itm/) of 75 /spl Aring/ thick nitrided-HIPOX oxide is about 2.0/spl times/10/sup 10/ cm/sup -2//spl middot/eV/sup -1/ which is comparable to that of control oxide grown by conventional thermal oxidation. The /spl Delta/D/sub itm/ of the nitrided-HIPOX oxide subjected to the stressing time of 1/spl times/10/sup 4/ sec under -0.1 A/cm/sup 2/ is 1.1/spl times/10/sup 11/ cm/sup -2//spl middot/eV/sup -1/ which is lower than that (1.5/spl times/10/sup 11/ cm/sup -2//spl middot/eV/sup -1/) of the control oxide under the same stressing condition.