Huang Jingyun

Structural Characterization and Photoluminescent Properties of Zn1-xMgxO Films on Silicon

Zn1-xMgxO films have been grown on silicon at various substrate temperatures by pulsed laser deposition. The structural and photoluminescent properties of films as a function of substrate temperature have been studied. The optimized substrate temperature is 650°C. The x-ray diffraction spectra indicate that the films are highly C-axis oriented, and no phase separation is observed. The crystal grain size of the films is about 100 nm as examined by atomic force microscopy. The cross-sectional transmission electron microscopy verified the C-axis orientation of the Zn1-xMgxO. These films showed ultraviolet photoluminescence at room temperature. The near-band-edge emission peak of the Zn1-xMgxO film deposited at 600°C has a blueshift (0.40 eV) larger than that of the film deposited at 500°C (0.33 eV). The ratio of the near-band-edge to defect level peak intensity is as large as 159.

Room-temperature electroluminescence of p-ZnxMg1 xO:Na/n-ZnO p-n junction light emitting diode

p-ZnxMg1−xO:Na/n-ZnO p–n junction light emitting diode (LED) was produced on n-ZnO (0001) single-crystal substrate using pulsed laser deposition. The realization of band gap engineering was achieved by the incorporation of Mg in ZnO layers and was confirmed by photoluminescence spectrum. The p-type ZnxMg1−xO:Na film with low resistance was obtained at 500 °C and in which, Na has taken effect evidenced by Hall and X-ray photo-electron spectroscopy measurements. The current-voltage curve of LED showed a rectifying behavior and obvious electroluminescence was realized by feeding a direct current up to 40 mA. Furthermore, its structural and electric characters are discussed as well.

Epitaxial Growth of High-Quality Silicon Films on Double-Layer Porous Silicon

The epitaxial growth of a high-quality silicon layer on double-layer porous silicon by ultra-high vacuum/chemical vapour deposition has been reported. The two-step anodization process results in a double-layer porous silicon structure with a different porosity. This double-layer porous silicon structure and an extended low-temperature annealing in a vacuum system was found to be helpful in subsequent silicon epitaxial growth. X-ray diffraction, cross-sectional transmission electron microscopy and spreading resistance testing were used in this work to study the properties of epitaxial silicon layers grown on the double-layer porous silicon. The results show that the epitaxial silicon layer is of good crystallinity and the same orientation with the silicon substrate and the porous silicon layer.

Structural and optical characterization of Zn1-xCdxO thin films deposited by dc reactive magnetron sputtering

Zn1-xCdxO crystal thin films with different compositions were prepared on silicon and sapphire substrates by the dc reactive magnetron sputtering technique. X-ray diffraction measurements show that the Zn1-xCdxO films are of completely (002)-preferred orientation for x less than or equal to 0.6. For x = 0.8, the Elm is a mixture of ZnO hexagonal wurtzite crystals and CdO cubic crystals. For pure CdO, it is highly (200) preferential-oriented. Photoluminescence spectrum measurement shows that the Zn1-xCdxO (x = 0.2) thin film has a redshift of 0.14 eV from that of ZnO reported previously.

GROWTH AND CHARACTERIZATION OF HIGH QUALITY SI1-X-YGEXCY ALLOY GROWN BY ULTRA-HIGH VACUUM CHEMICAL VAPOR DEPOSITION

High quality Si1-x-yGexCy alloy with 2.2% C is grown at a relatively high temperature (760°C) on Si(100) using ultra-high vacuum/chemical vapor deposition (UHV/CVD) system. The samples are investigated with high resolution cross-sectional transmission electron microscope and x-ray diffraction. Compared with Si1-xGex alloys, Si1-x-yGexCy alloys with small amounts of C have much less strain and larger critical layer thickness. The quality of interface is also improved. Relatively flat growing profiles of the film are confirmed by secondary ion mass spectroscopy. Fourier transform infrared spectroscopy is also used to testify that the carbon atoms are on the substitutional sites. It is proved that the UHV/CVD system is an efficient method of growing Si1-x-yGexCy alloys.