Bong-Jin Kim

Next generation of oxide photonic devices: ZnO-based ultraviolet light emitting diodes

Results are presented for ZnO-based ultraviolet light emitting diodes (LEDs) that employ a BeZnO∕ZnO active layer comprised of seven quantum wells. Arsenic and gallium are used for p-type and n-type layers. The ZnO-based LEDs show two dominant electroluminescence peaks located in the ultraviolet spectral region between 360 and 390nm, as well as a broad peak at 550nm.

Excitonic ultraviolet lasing in ZnO-based light emitting devices

The authors have fabricated ultraviolet (UV) laser diodes based on ZnO∕BeZnO films. The devices have p-n heterojunction structures with a multiple quantum well (MQW) active layer sandwiched between guide-confinement layers. The MQW active layer comprises undoped ZnO and BeZnO, while the two guide-confinement layers were As-doped p-type ZnO∕BeZnO and Ga-doped n-type BeZnO∕ZnO films, respectively. The exciton binding energy in the MQW region is exceptionally large (263meV). Exciton-related lasing was observed by optically pumping the MQWs. ZnO∕BeZnO-based diodes showed laser action by current injection at room temperature. The lasing mechanism is inelastic exciton-exciton collision.

Electrical charging of Au nanoparticles embedded by streptavidin-biotin biomolecular binding in organic memory device

In this study, electrical charging phenomena in an organic memory structure using Au nanoparticles (NPs) conjugated with a specific binding mechanism were demonstrated. Monolayer of streptavidin-passivated Au NPs was incorporated on biotin-coated SiO2 in structure of metal-pentacene-insulator-silicon (MPIS) device. Clockwise and counter-clockwise capacitance-voltage (C-V) hysteresis loops were measured depending on the oxide thickness. For 30 nm, a clockwise C-V hysteresis having memory window of 0.68 V was obtained under (+/−)12 V sweep range, while a counter-clockwise C-V hysteresis having memory window of 6.47 V was obtained under (+/−)7 V sweep range for 10 nm thick oxide.

Effects on Annealing Temperature for Solution-Processed IZTO TFTs by Nitrogen Incorporation

The effects on electrical properties of solution-processed indium zinc tin oxide (IZTO) thin film transistors (TFTs) by nitrogen incorporation were investigated as a function of annealing temperature. The nitrogen incorporation was controlled by NH 4 0H addition into a precursor solution of zinc, indium, and tin chlorides. At 600°C annealing, the nitrogen-doped IZTO TFTs showed a field-effect mobility of 5.33 cm 2 /V s with an on/off ratio of 2.05 × 10 7 , By the nitrogen incorporation, the annealing temperature could be lowered to 400°C for the fabrication of TFTs having a field-effect mobility of 0.303 cm 2 /V s. Physical and chemical analyses on films at various annealing temperatures were performed and compared, respectively.

Electrical properties of charging effect in Au nanoparticle memory device

Semiconductors or metal nanoparticles (NPs) using their monolayer bindings with self-assembly chemicals are an attractive topic for device researchers. Electrical performance of such structures can be investigated for a particular application, such as memory device. Currently, Au NPs has been reported to show a substantial potential in the memory applications. In this study, Au NP and gluing layer were fabricated through a new method of monolayer formation of a chemical bonding or gluing. In this study, a new NPs memory system was fabricated by using organic semiconductor, i.e., pentacene as the active layer, evaporated Au as electrode, SiO 2 as the gate insulator layer on silicon wafer. In addition, Au NPs coated with binding chemicals were used as charge storage elements on an APTES (3-amino-propyltriethoxysilane) as a gluing layer. In order to investigate chemical binding of Au NP to the gate insulator layer, GPTMS (3-glycidoxy-propyltrimethoxysilane) were coated on the Au NPs. As a result of that, a layer of gold nanoparticles has been incorporated into a metal-pentacene-insulator-semiconductor (MPIS) structure. The MPIS device with the Au NP exhibited a hysteresis in its capacitance versus voltage analysis. Charge storage in the layer of nanoparticles is thought to be responsible for this effect.