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Sn/Ge ratio in Ge1− y Sn y films on Si against the corresponding ratio in the gaseous mixture for the Ge2H6/SnD4 and Ge3H8/SnD4 deposition reactions. The data for the digermane process are limited to ratios below 5% Sn and temperatures below 355 °C due to the poor reactivity of the compound and inefficient growth rate of the crystal layer under lower temperatures below 330 °C. The solid line corresponds to r film = r gas. Growth temperatures are indicated by a color code. The inset shows the relative Ge incorporation efficiency K. The lines represent fits using an Arrhenius curve. The corresponding activation energies Ea are indicated in the diagram.
(a) Micrographs of a 250-nm-thick Ge0.92Sn0.08 layer. The phase-contrast image shows a flat surface and a uniform contrast microstructure indicating a homogeneous single-phase material. Threading dislocations and stacking faults are visible, particularly within the lower portion of the film. A high resolution image (inset) reveals a heteroepitaxial interface. (b) Micrograph of an annealed ∼350-nm-thick Ge0.93Sn0.07 layer doped with P. Inset is a magnified view (4×) of the interface showing a pseudo-periodic array of strain-relieving Lomer dislocations.
Top left: (224) RSM plots of RTA- processed Ge1− y Sn y films with 2.5%, 5.2% and 7.0% Sn. The relaxation line (double arrow) passes near the peak maximum, indicating mostly relaxed strain states in all cases. Top right: RBS spectra of as grown Ge0.945Sn0.055 and Ge0.91Sn0.09 films with thicknesses of 600 and 420 nm, respectively. Note that although the compositions are derived from a detailed fit of the entire spectrum, the intensities of the Sn signal scale linearly with Sn content. Bottom: Aligned and channeled spectra of an “as-grown” Ge0.02Sn0.08 layer. The ratio of the peak heights indicates that Sn occupies substitutional lattice sites.
Room temperature PL spectra from Ge1− y Sn y alloys on Si substrates, generated with 980 nm laser excitation. The maxima of all curves have beennormalized to facilitate the comparison between different Sn concentrations. The inset shows the spectrum from an n-type sample with n = 2 × 1019 cm−3.
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