Zhao Bing-hui

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.

Identification of Acceptor States in Li–N Dual-Doped p-Type ZnO Thin Films

Li–N dual-doped p-type ZnO (ZnO:(Li,N)) thin films are prepared by pulsed laser deposition. The optical properties are studied using temperature-dependent photoluminescence. The LiZn–NO complex acceptor with an energy level of 138 meV is identified from the free-to-neutral-acceptor (e, A0) emission. The Haynes factor is about 0.087 for the LiZn–NO complex acceptor, with the acceptor bound-exciton binding energy of 12meV. Another deeper acceptor state located at 248meV, also identified from the (e, A0) emission, is attributed to zinc vacancy acceptor. The two acceptor states might both contribute to the observed p-type conductivity in ZnO:(Li,N).

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.

Structural and Photoluminescence Characterization of GaN Film Grown on Si(111)Substrate

GaN epilayer grown on Si (111) substrate by a novel vacuum reaction method rather than metal organic chemical vapor deposition or molecule beam epitaxy is reported. Scanning electron micrograph shows that surface of GaN film is flat and crack-free. A pronounced GaN (0002) peak appears in the x-ray diffraction pattern. The full width at half-maximum (FWHM) of the double-crystal x-ray rocking curve for (0002) diffraction from the GaN epilayer is 30 arcmin. The photoluminescence spectrum shows that the GaN epilayer emits light at the wavelength of 365 nm with an FWHM of 8 nm (74.6 meV).

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.