Crystallization of Electrodeposited Germanium Thin Film on Silicon (100)

Abstract

We report the crystallization of electrodeposited germanium (Ge) thin films on n-silicon (Si) (100) by rapid melting process. The electrodeposition was carried out in germanium (IV) chloride: propylene glycol (GeCl4:C3H8O2) electrolyte with constant current of 50 mA for 30 min. The measured Raman spectra and electron backscattering diffraction (EBSD) images show that the as-deposited Ge thin film was amorphous. The crystallization of deposited Ge was achieved by rapid thermal annealing (RTA) at 980 °C for 1 s. The EBSD images confirm that the orientations of the annealed Ge are similar to that of the Si substrate. The highly intense peak of Raman spectra at 300 cm−1 corresponding to Ge-Ge vibration mode was observed, indicating good crystal quality of Ge. An additional sub peak near to 390 cm−1 corresponding to the Si-Ge vibration mode was also observed, indicating the Ge-Si mixing at Ge/Si interface. Auger electron spectroscopy (AES) reveals that the intermixing depth was around 60 nm. The calculated Si fraction from Raman spectra was found to be in good agreement with the value estimated from Ge-Si equilibrium phase diagram. The proposed technique is expected to be an effective way to crystallize Ge films for various device applications as well as to create strain at the Ge-Si interface for enhancement of mobility.

The Effects of Annealing Temperatures on Composition and Strain in SixGe1−x Obtained by Melting Growth of Electrodeposited Ge on Si (100)

“…Here, it can be seen that the Si fraction increases with the increase of temperature. In our previous report [ 40 ] where an annealing was performed at 980°C (Ge thickness =160 nm), the Si fraction seems to be much lower compared to the present samples. We speculate that Ge thickness may have significant role in suppressing the diffusion of Si atoms into Ge region, thus, affecting the overall diffusion rate in Si x Ge 1− x .…”

“…Prior to deposition, Si substrates were cleaned by standard RCA process and diluted hydrofluoric (HF) acid to remove native oxide layer. The deposition was carried out in a mixture of 5% GeCl 4 in C 3 H 8 O 2 where Si substrate was set as a cathode and Pt wire as an anode [ 40 , 46 ]. The process was done at room temperature with the applied current density of 20 mA/cm 2 for 30 min.…”

“…The crystallization of deposited Ge can be easily achieved by applying a so-called rapid melting process [ 18 , 37 ]. By applying such high annealing temperatures, the intermixing Si-Ge was observed at Ge/Si interface [ 38 – 40 ]. To date, a great deal of intensive theoretical and experimental studies related to Ge/Si interface have been reported [ 27 , 39 , 41 , 42 ].…”

“…Recently, we demonstrated the electrodeposition of Ge films on Si (100) by using an electrolyte formed by a mixture of GeCl 4 and propylene glycol, C 3 H 8 O 2 and their subsequent crystallization process was successfully achieved by rapid melting process at 980°C for 1 s [ 40 ]. It has been observed that the Si-Ge intermixing occurred at Ge/Si, as indicated by Raman spectra and depth profile analysis.…”

Mechanism of Liquid-Phase Reductive Thin-Film Deposition under Quasiballistic Electron Incidence

“…Thus, it is difficult to avoid contaminations at electroplating of thin Si and Ge films. [15][16][17][18][19][20][21][22][23][24][25] In the case of quasiballistic electron incidence, on the contrary, reduction directly proceeds without any counter electrodes. Thin films with fewer contaminations can be formed due to no gas evolutions.…”