A1P nanocrystals embedded in silica glasses were prepared via an easy sol-gel process. The gels synthesized by the hydrolysis of a complex solution of Si (OC2H5) 4, A1 (NO3)3 Æ9H2O and PO (OC2H5) 3 were heated at 600℃ for 10h in an air atmosphere to form an Al2O3-P2O5-SiO2 gel glass. The gel glasses were then heated in the presence of H2-N2 mixed gas, in which the P(V) are reduced by the H2 gas, and react with Al (Ⅲ) to form fine cubic A1P crystallites embedded in silica glasses. The X-ray diffraction patterns showed (111), (220), and (311) diffraction lines from cubic AlP crystals. The AlP (220), (311), (422), and (440) diffraction lines were observed in the electron diffraction pattern. The size of AlP nanocrystals was found to be from 5 to 10nm in diameter by transmission electron microscopy. A strong room temperature photoluminescence (PL) with peaks at 533, 582, 649, and 688nm was observed from AlP/SiO2 nanocomposites. The PL is suggested to originate from the hydrogen-related species (PL band at 533nm), the small "peroxy radical" (PL band at 582nm), and the nonbridging oxygens (PL bands at 649 and 688nm), respectively.

Measured and calculated (without any adjustable material parameter) electron Hall mobility and carrier concentration in the range of 26.5-73K are reported for a high-mobility free-standing bulk GaN grown by hydride vapor phase epitaxy. The peak electron mobility of 7386cm2/Vs at 48K and a value of 1425cm2/V s at 273K were measured. An iterative solution of the Boltzmann equation was applied to calculate the mobility using the materials parameters either measured on the sample under study or recent values that are just becoming available with only the acceptor concentration being variable. Using only one donor and one conducting layer system, the donor and acceptor concentrations of 1.76

The polarity of GaN films grown using GaN and AlN buffer layers on sapphire substrates by molecular beam epitaxy were investigated by atomic force microscopy, hot wet chemical etching, and reflection high-energy electron diffraction. We found that the GaN films grown on high temperature AlN (>890℃) and GaN (770-900℃) buffer layers invariably show Ga and N polarity, respectively. However, the films grown using low temperature (500℃) buffer layers, either GaN or AlN, could have either Ga or N polarity, depending on the growth rate of the buffer layer