We report a lateral Ge-on-Si ridge waveguide light emitting diode （LED） grown by ultrahigh vacuum chemical vapor deposition （UHV-CVD）. Direct-bandgap electroluminescence （EL） of Ge waveguide under continuous current is observed at room temperature. The heat-enhancing luminescence and thermal radiation-induced superlinear increase of edge output optical power are found. The spontaneous emission and thermal radiation based on the generalized Planck radiation law are calculated and fit very well to the experimental results. The Ge waveguides with different lengths are studied and the shorter one shows stronger EL intensity.
High-performance Ge n~＋/p junctions were fabricated at a low formation temperature from 325℃ to 400℃ with a metal（nickel）-induced dopant activation technique. The obtained Ni Ge electroded Ge n＋/p junction has a rectification ratio of 5.6×10~4 and a forward current of 387 A/cm^2at -1 V bias. The Ni-based metal-induced dopant activation technique is expected to meet the requirement of the shallow junction of Ge MOSFET.
Polycrystalline Ge1-xSnx（poly-Ge1-xSnx） alloy thin films with high Sn content（〉 10%） were fabricated by cosputtering amorphous GeSna-GeSn on Ge100 wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm^2 to 550 mJ/cm^2. High quality poly-crystal Ge0.90 Sn0.10 and Ge0.82 Sn0.18 films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain,and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum（FWHM） is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge1-xSnx by Raman spectra.
Plasma treatment and 10% NH_4OH solution rinsing were performed on a germanium（Ge） surface.It was found that the Ge surface hydrophilicity after O_2 and Ar plasma exposure was stronger than that of samples subjected to N_2 plasma exposure. This is because the thin Ge Ox film formed on Ge by O_2 or Ar plasma is more hydrophilic than Ge Ox Ny formed by N_2 plasma treatment. A flat（RMS 〈 0：5 nm） Ge surface with high hydrophilicity（contact angle smaller than 3°） was achieved by O_2 plasma treatment, showing its promising application in Ge low-temperature direct wafer bonding.
The influence of defects in low temperature Ge layer on electrical characteristics of p-Ge/i-Ge/n-Si and n-Ge/i-Ge/p-Ge photodiodes（PDs） was studied.Due to a two-step growth method,there are high defect densities in low-temperature buffer Ge layer.It is shown that the defects in low-temperature Ge layer change the band diagrams and the distribution of electric field,leading to the increase of the total dark current for p-Ge/i-Ge/n-Si PDs,whereas these defects have no influence on the dark current for n-Ge/i-Ge/p-Ge PDs.As a complement,a three-dimensional simulation of the total current under illumination was also performed.
Xiaohui YiZhiwei HuangGuangyang LinCheng LiSongyan ChenWei HuangJun LiJianyuan Wang
