Chia-Hsuan Hu

InGaN/GaN single-quantum-well microdisks

We have grown In{sub x}Ga{sub 1-x}N/GaN quantum wells atop GaN microdisk with {gamma}-LiAlO{sub 2} substrate by using plasma-assisted molecular beam epitaxy. The structural and optical properties of the samples were analyzed by transmission electron microscopy, x-ray diffraction, cathodoluminescence, and photoluminescence measurements. Based on the measured results, we obtained the indium concentration of the In{sub x}Ga{sub 1-x}N/GaN single quantum well to be x = 0.25 with a band-gap energy of 2.31 eV, which is consistent with the bowing effect of bulk In{sub x}Ga{sub 1-x}N: E{sub g}(x) = [3.42 - x * 2.65 - x * (1 - x) * 2.4] eV.

Green light emission by InGaN/GaN multiple-quantum-well microdisks

The high-quality In{sub x}Ga{sub 1−x}N/GaN multiple quantum wells were grown on GaN microdisks with γ-LiAlO{sub 2} substrate by using low-temperature two-step technique of plasma-assisted molecular beam epitaxy. We demonstrated that the hexagonal GaN microdisk can be used as a strain-free substrate to grow the advanced In{sub x}Ga{sub 1−x}N/GaN quantum wells for the optoelectronic applications. We showed that the green light of 566-nm wavelength (2.192 eV) emitted from the In{sub x}Ga{sub 1−x}N/GaN quantum wells was tremendously enhanced in an order of amplitude higher than the UV light of 367-nm wavelength (3.383 eV) from GaN.

Growth of InN hexagonal microdisks

InN hexagonal thin wurtzite disks were grown on γ-LiAlO2 by plasma-assisted molecular-beam epitaxy at low temperature (470oC). The (0001¯) InN thin disk was established with the capture of N atoms by the β¯-dangling bonds of most-outside In atoms, and then the lateral over-growth of the In atoms were caught by the β¯-dangling bonds of the N atoms. From the analyses of high-resolution transmission electron microscopy, the lateral over-grown width was extended to three unit cells at [11¯00]InN direction for a unit step-layer, resulting in an oblique surface with 73o off c-axis.

Electrical contact for wurtzite GaN microdisks

We developed a back processing to fabricate an electrical contact of wurtzite GaN microdisk on transparent p-type GaN template. The interface welding between the GaN microdisk and p-type GaN template produced a very solid and secure epi-film contact for the electrical current passing through, with a resistance of 45.0 KΩ and threshold voltage of 5.9 V. The back processing can resolve the obstacle of electrical contacts for self-assembled wurtzite nano-devices.

Growth of InGaN/GaN quantum wells with graded InGaN buffer for green-to-yellow light emitters

We have studied the growth of high-indium-content In x Ga1− x N/GaN double quantum wells (QWs) for yellow and green light emitters by plasma-assisted molecular beam epitaxy at a low substrate temperature (570 °C). By introducing a graded In y Ga1− y N buffer layer, the PL intensity of QWs can be increased sixfold compared with that of the original structure. In addition, the indium content in InGaN QWs was increased owing the prolonged growth time of the graded In y Ga1− y N buffer layer. After adjusting to optimal growth conditions, we achieved In x Ga1− x N/GaN QWs with x = 0.32. Photoluminescence measurements showed that the emission wavelength from In x Ga1− x N/GaN QWs was 560 nm (2.20 eV). The optimal condition for the gradient In y Ga1− y N buffer layer was obtained for light emission from green to yellow.

Silicon doping of InP using modified flow rate modulation epitaxy

Abstract In this study, silicon doping using flow rate modulation epitaxy was found to produce better characteristics compared with conventional metal-organic chemical vapor deposition of the same growth system. The amount of phosphine is very critical in this new growth method. A lower compensation ratio (0.1) and higher mobility (3200 cm 2 V −1 s −1 at 300 K) are obtained under the optimum conditions. These are very important for application to high speed and low noise devices.

Metalorganic chemical vapor deposition of InP using phosphine modulation

In this study, a new epitaxial growth process was developed using phosphine modulation using conventional metalorganic chemical vapor deposition. With this method, phosphine was switched off a short time in each cycle and provided a metal‐rich growth surface. With higher surface mobility of indium atoms than that of InP molecules, crystal quality was improved significantly. Photoluminescence full width at half‐maximum 5.6 meV at 77 K was achieved under optimum growth conditions.

MOCVD growth of InP by phosphine modulation

A new epitaxial growth process was developed using phosphine modulation using conventional metal-organic chemical vapor deposition (MOCVD). With this method, phosphine was switched off a short time in each cycle and provided a metal-rich growth surface. With higher surface mobility of indium atoms than that of InP molecules, crystal quality was improved significantly. Photoluminescence full width at half maximum of 5.6 meV at 77 K was achieved under optimum growth conditions.<<ETX>>