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The ZnO films were grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) using dimethylzinc (DMZn) and oxygen. The as-grown film has strong (0002) oriented characteristic, containing the chain-like network grains in small sizes, A well-resolved shoulder emission at 3.03 eV in the photoluminescence (PL) spectra has been ascribed to the interstitial zinc in the crystal, implying a serious oxygen deficiency state of the MOCVD growth, in good agreement with the analysis of XPS results. Post-annealing of the films leads to the remarkable improvement of the structure, morphology, components and optical properties. Large hexagonal columnar grains were then observed by atomic force microscope (AFM). The luminescence efficiency was enhanced greatly due to the reduction of the nonradiative defects. Meanwhile, chemisorbed oxygen gives rise to surface acceptor states, resulting in the different radiative recombination. Photoluminescence excitation measurement shows good agreement with the above conclusions. [ABSTRACT FROM AUTHOR]

Quantum and transport scattering times related to different subbands in modulation-doped Al0.22Ga0.78N/GaN single quantum wells (SQW) have been studied by magneto- transport measurements. The quantum scattering time related to the first and the second subbands is determined to he 0.078 ps and 0.088 ps, respectively, at 1.5 K. Results indicate that the scatterings from heterointerface and ionized donors at both side of GaN well are all important in limiting quantum scattering time. By using mobility spectrum technique the transport scattering time related to the first subband is determined to he 0.128 ps. Transport-to-quantum scattering time ratio in the first subband is 1.6. It is concluded the large angle scatterings play a very important role in limiting quantum scattering time in this SQW. [ABSTRACT FROM AUTHOR]

Abstract. The impact of device scaling on modern MOS technology is discussed in terms of the random telegraph signals (RTSs) and low-frequency noise in n-MOSFETs with gradually decreased channel widths. RTSs with very large amplitude (> 60%) am observed in the devices with ultra-narrow channels at room temperature for the first time. Furthermore, low-frequency noise spectra having both 1/f' and Lorentzian type are found separately in the same ultra-narrow channel at different gate bias voltage, whereas only 1/f' noise is observed in relatively wide channels. The observations strongly suggest that low-frequency noise in weak inversion dominantly suffer from carrier mobility fluctuation rather than carrier number fluctuation in ultra-narrow channels, which is confirmed by numerical simulations. [ABSTRACT FROM AUTHOR]

Abstract. The oxidation of GaN epilayers in dry oxygen has been investigated. The GaN epilayers, about 1 micro m thick, were grown on (0001) sapphire substrates by rapid thermal process/low pressure metalorganic chemical vapor deposition. Bulk theta - 2 theta X-ray diffraction (XRD) data showed that the slight oxidation of GaN began to occur at 800 Celsius tot 6 h. The oxide was identified as the monoclinic beta-Ga[sub 2]O[sub 3]. The GaN epilayers were completely oxidized at 1050 Celsius for 4 h or at 1100 Celsius for I h. For all samples, the strongest oxide's peak is (11-3), and (30-6) followed. There is a rapid oxidation process in the initial stage of oxidation, and a relatively slow process followed when the temperature was over 1000 Celsius. The oxidation of two stages was limited by the rate of an interracial reaction mechanism and by the diffusion mechanism, respectively. When the temperature reaches 1100 Celsius, the oxidation rate is very fast, which is considered as the results of the GaN decomposition at high temperature under atmosphere. The oxide layers were also observed by a scanning electron microscope, which shows a rough oxide surface and an expansion of the volume of 40%. The photoluminescence (PL) seriously influenced by the oxidation is also discussed. [ABSTRACT FROM AUTHOR]

Raman scattering from an AlGaN/GaN heterostructure was performed in the temperature range from 77 to 773 K. The first- and second-order Raman scattering of the A1 longitudinal-optical phonon-plasmon coupled mode from an AlGaN/GaN interface as well as the Raman scattering from the GaN layer were observed. All the modes downshift, and their intensities weaken with increasing temperature. The free-carrier concentration estimated by the frequency of the coupled mode from an AlGaN/GaN interface is 7.5 times as high as that of n-AlGaN, indicating mass free-carrier transfer from the AlGaN barrier to the GaN well. Moreover, the temperature dependence of the phonon frequency is well described by an empirical formula. [ABSTRACT FROM AUTHOR]

Abstract. Si-based metal-ferroelectric-semiconductor (MFS) structures without buffer layers between Si and ferroelectric films have been developed by depositing SrBi[sub 2]Ta[sub 2]O[sub 9] (SBT) directly on n-type (100)-oriented Si. Some effective processes are adopted to improve the electrical properties of these MFS structures. Contrary to the conventional MFS structures with top electrodes directly on ferroelectrics, our MFS structures have been developed with thin dense SiO[sub 2] films deposited between ferroelectric films and top electrodes. Due to the SiO[sub 2] films, the leakage current densities of MFS structures are reduced to 2 x 10[sup -8] A/cm[sup 2] under the bias of 5 V. The C - V electrical properties of the MFS structures are greatly improved after annealing at 400 Celsius in N[sub 2] ambient for 1 h. The C - V memory windows are increased to 3 V, which probably results from the decrease of the interface trap density at the Si/SBT interface. [ABSTRACT FROM AUTHOR]

Abstract. Ge-rich Ge[sub 1-x-y]Si[sub x]C[sub y] alloys have been grown on Si (100) substrates by plasma-enhanced rapid thermal chemical vapor deposition. It is found that there is a strong suppressive effect of C on the Ge composition and the growth rate. A possible mechanism for the suppressive effect is proposed. After calculations of atomic configuration, we obtain the relationship between the degree of suppression and the Ge/C atomic ratio. From the calculation results, a saturation tendency of the suppressive effect is expected with increasing Ge concentration in the growth of Ge[sub l-x-y]Si[sub x]C[sub y] alloys. [ABSTRACT FROM AUTHOR]