Yung-Hsiang Lin

Effects of the material polarity on the green emission properties of InGaN∕GaN multiple quantum wells

Green-light-emission InGaN∕GaN multiple quantum wells (MQWs) with different polarities were grown by metal organic chemical vapor deposition. A clear phase separation was observed both in the Ga- and N-polarity samples by high resolution transmission electron microscopy, corresponding to two InGaN-related emissions (In-rich dots and an InGaN matrix) seen in photoluminescence spectra. The dot-related emission in the Ga-polarity MQWs shows stronger carrier localization, as well as a weak influence of defects and temperature insensitivity, when compared to the N-polarity MQWs. In addition, efficient carrier transport, from the low-indium InGaN matrix to high-indium In-rich dots, was observed in the Ga-polarity structure, enhancing the function of quantum-dot structures with Ga polarity, and resulting in a high quantum yield of green light emission.

Device Characteristics of AlGaN/GaN MOS-HEMTs Using High-

In this brief, AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) using an electron-beam-evaporated praseodymium oxide layer (Pr₂O₃) in a high-oxygen-flow environment during the gate-dielectric-layer formation was studied. By adjusting the oxygen flow rate in an electron-beam evaporator chamber, the highest Pr content in Pr₂O₃ occurred at 15 sccm. Moreover, the Pr₂O₃ thin film also achieved a good thermal stability after 400-degC, 600-degC, and 800-degC postdeposition annealing due to its high-binding-energy (933.2 eV) characteristics. The gate leakage current can be improved significantly by inserting this high- <i>k</i> dielectric layer, and meanwhile, the power-added efficiency can be enhanced up to 5%. Experimental results have also shown that Pr₂O₃ MOS-HEMTs outperformed the standard GaN HEMTs in output power density and in pulsed-mode operation. These high-performance electron-beam-evaporated Pr₂O₃ high-<i>k</i> AlGaN/GaN MOS-HEMTs are suitable for high-volume production due to its <i>in</i> <i>situ</i> insulator and metal-gate deposition in the same chamber.

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We have studied the characteristics of blue InGaN∕GaN multiquantum-well light-emitting diodes (LEDs) after reducing the length of the lateral current path through the transparent layer through formation of a peripheral high-resistance current-blocking region in the Mg-doped GaN layer. To study the mechanism of selective activation in the Mg-doped GaN layer, we deposited titanium (Ti), gold (Au), Ti∕Au, silver, and copper individually onto the Mg-doped GaN layer and investigated their effects on the hole concentration in the p-GaN layer. The Mg-doped GaN layer capped with Ti effectively depressed the hole concentration in the p-GaN layer by over one order of magnitude relative to that of the as-grown layer. This may suggest that high resistive regions are formed by diffusion of Ti and depth of high resistive region from the p-GaN surface depends on the capped Ti film thickness. Selective activation of the Mg-doped GaN layer could be used to modulate the length of the lateral current path. Furthermore, the ...

Praseodymium Oxide Layer

In this study, we used the selective ring-region activation technique to restrain the surface leakage current and to monitor the luminescence characteristics of InGaN-GaN multiple quantum-well blue light-emitting diodes (LEDs). To access the current blocking region after forming a periphery high-resistance ring-region of the Mg-doped GaN layer and to reduce the degree of carrier trapping by the surface recombination centers, we deposited a titanium film onto the Mg-doped GaN epitaxial layer to form a high-resistance current blocking region. To characterize their luminescence performance, we prepared LEDs incorporating titanium films of various widths of the highly resistive current blocking layer. The hole concentration in the Mg-doped GaN epitaxial layer decreased from 3.45times1017 cm-3 to 3.31times1016cm-3 after capping with a 250-nm-thick layer of titanium and annealing at 700 degC under a nitrogen atmosphere for 30 min. Furthermore, the luminescence characteristics could be improved by varying the width of the highly resistive region of the current blocking area; in our best result, the relative electroluminescence intensity was 30% (20 mA) and 50% (100 mA) higher than that of the as-grown blue LEDs

Enhanced characteristics of blue InGaN/GaN light-emitting diodes by using selective activation to modulate the lateral current spreading length

Recently, gallium nitride (GaN) substrates have been widely used in high-power monolithic microwave integrated circuit applications, which work because of the high breakdown voltage associated with the wider energy band-gap. The objective of this article is to investigate the spiral inductors that have been used to implant various ions on GaN substrates, demonstrated separately by N+, Mg+ and O+. The measured substrate resistance (R sub) results were 85 Ω and 360 Ω for undoped GaN substrates and N+ doped substrates, respectively. This ion implantation technology could substantially improve the substrate resistance and provide a higher quality factor value (Q-value) for spiral inductors. The low parasitic effect extracted by the scattering parameter (S-parameter) for various substrates indicated that the spiral inductor value can be applied stably at high frequency. Consequently, the high GaN substrate quality adopting high-isolation ion implantation technology, demonstrates its huge potential for high-power and high-efficiency amplifier applications.

Improving the Luminescence of InGaN–GaN Blue LEDs Through Selective Ring-Region Activation of the Mg-Doped GaN Layer

In this study, the LED samples were grown by metalorganic chemical vapor deposition (MOCVD) on 430 mum-thick c-plan sapphire substrates. The layer sequence consisted of a 25.0 nm GaN nucleation layer followed by a 2.0 mum-thick undoped GaN buffer layer, a 2.0 mum-thick Si-doped GaN conduction layer, a active region composed of five 2.5 nm-thick In0.23Ga0.77N QWs separated by 12.0 nm-thick GaN barriers, followed by 15 pairs of Mg-doped AlGaN/GaN superlattice structure consisting of 3.0 nm AlGaN layers, and 3.0 nm GaN layers, a 30.0 nm-thick Mg-doped GaN cap layer. Finally, a 10.0 nm Mg-doped GaN contact layer was grown on the top of LED.

An improved passive inductor microwave performance on gallium nitride substrates using ion implantation technology

In this study, we used the selective ring-region ion implantation technique to restrain the surface leakage current and to monitor the luminescence characteristics of InGaN/GaN multiple quantum-well blue light-emitting diodes (LEDs). The luminescence characteristics could be improved by varying the width of the highly resistive region of the current blocking area; and the leakage current also can be reduced.

Minor magnesium doping in P-type layer of InGaN/GaN MQW LED to enhance electrical and optical properties

In this work, we modified the p-type epitaxy structure to improve the p-type metal-semiconductor ohmic contact. Further, we investigated the electrical and optical properties by adjusting the p-type cladding layer structure in the InGaN/GaN MQW samples.