Abstract
High-quality single-crystal-like Ge (004) thin films have been epitaxially grown using radio-frequency magnetron sputtering on Si (001) substrates successfully. The crystalline quality of the Ge films can be obviously improved by applying a positive bias on the substrate holder. X-ray diffraction measurements show that the single-crystal-like Ge film has a narrow full width at half maximum of 0.26°. The perpendicular lattice constant (aGe⊥) and in-plane lattice constant (aGe∥) are 0.5671 and 0.564 nm. The Raman shift full width at half maximum shows that the defects in the film are obviously reduced. Transmission electron microscopy diffraction patterns also show that the Ge (004) film has good crystalline quality. The results can be applied as Ge buffer layers on Si substrates for the fabrication of high-efficiency III–V solar cells and photodetectors.
Highlights
The high near-infrared absorption property of Ge material has been widely used in III–V multijunction solar cells and photodetectors [1,2,3,4]
The Ge film on Si substrate produced by reduced pressure chemical vapor deposition (RPCVD) has the smallest full width at half maximum (FWHM) value of X-ray diffractometer (XRD) and root mean square (RMS) value of the atomic force microscope (AFM), which is currently the best Ge film epitaxial method [8,9]
It is determined that the Ge thin film is a single crystalline
Summary
The high near-infrared absorption property of Ge material has been widely used in III–V multijunction solar cells and photodetectors [1,2,3,4]. Chemical vapor deposition (CVD) is the most popular method [7]. The Ge film on Si substrate produced by reduced pressure chemical vapor deposition (RPCVD) has the smallest full width at half maximum (FWHM) value of X-ray diffractometer (XRD) and root mean square (RMS) value of the atomic force microscope (AFM), which is currently the best Ge film epitaxial method [8,9]. Electron cyclotron resonance chemical vapor deposition (ECR-CVD) process temperature is the lowest, and its FWHM of XRD, at a very thin epitaxial thickness, has a lower value [10]. PVD process is not an easy method to fabricate epitaxial Ge films. The epitaxial growth of a high-quality single-crystal-like Ge film on a Si substrate without an annealing process is important.
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