Microstructure of non-polar GaN on LiGaO2 grown by plasma-assisted MBE
We have investigated the structure of non-polar GaN, both on the M - and A-plane, grown on LiGaO2 by plasma-assisted molecular beam epitaxy. The epitaxial relationship and the microstructure of the GaN films are investigated by transmission electron microscopy (TEM). The already reported epi-taxial relationship and for M -plane GaN is confirmed. The main defects are threading dislocations and stacking faults in both samples. For the M -plane sample, the density of threading dislocations is around 1 × 1011 cm-2 and the stacking fault density amounts to approximately 2 × 105 cm-1. In the A-plane sample, a threading dislocation density in the same order was found, while the stacking fault density is much lower than in the M -plane sample.
Growth and characterization of a-plane (112¯0) GaN films on (010) LiGaO2 substrate by chemical vapor deposition
Nonpolar (112¯0) GaN films were successfully grown on closely lattice-matched (010) LiGaO2 (LGO) substrates by chemical vapor deposition (CVD) method. The dependence of growth characteristics on the growth temperatures was investigated. The surface morphologies of GaN films were characterized by scanning electron microscopy. Structural properties of the GaN epilayers were investigated by X-ray diffraction and transmission electron microscopy. Cross-section transmission electron microscopy results showed direct evidence of the in-plane structural relationship between the GaN epilayer and (010) LGO substrate. Low temperature photoluminescence was dominated by neutral donor bound excitons emission at 3.472 eV and the defect-related yellow emission was negligible.
Application of 2μm Tm Laser on Biomedicine
Continuous wave Thulium laser emits at wavelength of 2.0 mm, which is well suited for tissue ablationand thermally stimulating cutaneous nerves due to its high absorption by water. 2 mm laser can be transmitted suffi-ciently by common quartz fibers and it is safe for eyes. A brief introduction of principle of 2 mm CW Tm Laser is giv-en, analyzing the photothermal modeling of thulium laser-tissue interaction, comparing 2 mm CW Tm Laser with tradi-tional laser.