Kun-Feng Chien

Improvement of defect reduction in semi-polar GaN grown on shallow-trenched Si(001) substrate

The improved design of sub-micron trenches on Si(001) substrate was demonstrated for defect suppression in semi-polar selectively-grown GaN layers. Cathodoluminescence and transmission electron microscopy measurements revealed a dramatically decreased density of threading dislocations and stacking faults near the surface of the overgrown GaN layer when the trench width ranged from 500 to 1500 nm. It was observed that defects were effectively trapped inside the trench when the ratio of trench depth to the SiO2 thickness is less than 0.66. In addition, a significant reduction of intrinsic polarization electric field was achieved for the InGaN/GaN multiple quantum well on the GaN selectively grown from the Si trenches.

Optical and Magnetic Properties of Grown by Plasma-Assisted Molecular Beam Epitaxy

Zn1-xMnxO films (0 ≤ ×≤ 0.070) were grown by plasma-assisted molecular beam epitaxy on Si substrates with AlN buffer layers. For low Mn concentration samples, x ≤ 0.02, photoluminescence spectra show strong near band edge emission. Strong phonon and exciton coupling-induced resonant Raman scattering was observed. Paramagnetic, antiferromagnetic, and ferromagnetic phases were observed. Room temperature ferromagnetism for all samples was attributed to the bound magnetic polaron effect.

Optical and Magnetic Properties of

Zn1-xMnxO films (0 ≤ ×≤ 0.070) were grown by plasma-assisted molecular beam epitaxy on Si substrates with AlN buffer layers. For low Mn concentration samples, x ≤ 0.02, photoluminescence spectra show strong near band edge emission. Strong phonon and exciton coupling-induced resonant Raman scattering was observed. Paramagnetic, antiferromagnetic, and ferromagnetic phases were observed. Room temperature ferromagnetism for all samples was attributed to the bound magnetic polaron effect.

{\rm Zn}_{1-x}{\rm Mn}_{x}{\rm O}

Zn1-xMnxO films (0 ≤ ×≤ 0.070) were grown by plasma-assisted molecular beam epitaxy on Si substrates with AlN buffer layers. For low Mn concentration samples, x ≤ 0.02, photoluminescence spectra show strong near band edge emission. Strong phonon and exciton coupling-induced resonant Raman scattering was observed. Paramagnetic, antiferromagnetic, and ferromagnetic phases were observed. Room temperature ferromagnetism for all samples was attributed to the bound magnetic polaron effect.

Grown by Plasma-Assisted Molecular Beam Epitaxy

The strains in GaAs nanowires, which were grown from 1700- to 80-nm-wide trenches on the Si(001) wafer with SiO2 masks, were investigated by cathodoluminescence. For 1700- to 500-nm-wide trenches, the in-plane tensile strain at 15 K decreases with the decreasing trench width. The strain increases abruptly when the trench width is 300 nm, and then decreases as the trench width is further decreased. The results revealed that the stress induced by the SiO2 sidewalls dominates when the width is less than the depth of the trench. This approach provides an effective technique to measure the strain of a single nanowire and helps for the demonstration of selectively-grown GaAs with a designed strain.