Nanoscale GaN quantum dots were fabricated on AlxGa1−xN layer surfaces via metalorganic chemical vapor deposition. In order to achieve a self-assembling dot structure, a two-dimensional growth mode (step flow) of GaN films on AlxGa1−xN (x=0–0.2) surfaces that is energetically commenced under the conventional growth conditions was intentionally modified into a three-dimensional mode by using a ‘‘surfactant.’’ The surfactant is believed to inhibit the GaN film from wetting the AlGaN surface due to the change in surface free energy. The resulting morphological structures of GaN dots were found to be sensitive to the doping rate of tetraethyl silane used as a surfactant, the Al content (x) of the AlxGa1−xN layer, and the growth temperature. A very intense photoluminescence emission was observed from the GaN dots embedded in the AlGaN layers.

A method of alternative co-doping in metal organic chemical deposition was used to realize high hole carrier concentrations of about 6 × 1018/cm3 in AlxGa1−xN (x = 0.4) and 2 × 1019/cm3 for GaN at room temperature. This technique opens up a new avenue for fabricating electronic p-channel devices, such as p-channel high electron mobility transistor, and vertical current flow type devices, such as deep ultra violet light emitting diodes.

Nanoscale GaN dots were successfully formed on AlxGa1−xN/6H-SiC(0001) surfaces by gas-source molecular beam epitaxy. It was found that the growth mode can be changed by introducing Si before GaN growth, where the Si is believed to play an important role in the change of the AlxGa1−xN surface free energy. Without introducing Si, the GaN growth mode was two dimensional and (1×3) reconstruction was observed. The growth mode of GaN was changed from two-dimensional to three-dimensional by introducing Si on the AlxGa1−xN surface. In situ reflection high-energy electron diffraction and atomic force microscopy observations were used to monitor and characterize the growth processes and surface morphology.

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The wavelength of laser emission from an electron-beam-pumped ZnO was measured in the temperature range from 82 to 250°K. The laser emission occurred near the line due to the annihilation of a free exciton assisted by one LO phonon at 82°K. Above 180°K the laser emission occurred near the line due to the transition assisted by two LO phonons. From 130 to 170°K the laser oscillation appeared in two spectral lines. The temperature dependence of threshold current density measured from 82 to 250°K was weak compared with the theoretical curve based on the laser action involving the A-LO line.