Strain-Controlled of Compressive/Tensile Ge Epilayers on Si by Electron Cyclotron Resonance Chemical Vapor Deposition

Abstract

In this study, we use electron cyclotron resonance chemical vapor deposition to investigate the strain behavior in Ge epilayers grown on silicon at a low temperature of 220°C. The strain in the Ge epilayers is transformed from compressive (−0.567%) to tensile (0.15%) as the process pressure decreases and main coil current increases. This tensile strain is due to intrinsic stress in the Ge epilayers at high process pressure and low main coil current. Besides, the Ge atoms have higher kinetic energy and shorter mean free path at low process pressure and high main coil current, which causes atomic bombardment effect on the Ge surfaces frequently. Thus, the intrinsic stress in Ge epilayers become compressive. The absorption coefficient of tensile and compressive strain in Ge films are measured using a UV–VIS-NIR spectrophotometer. The results show the absorption coefficients of the tensile strain Ge epilayer has a redshift condition on the absorption edge compare with compressive strain Ge epilayers. Finally, the structure information of the Ge epilayers is identified by atomic force microscopy and transmission electron microscopy. This strain control technology is modulated by film growth parameter, which can adjust the Ge bandgap for the device requirement.

Effect of Substrate Biasing on the Epitaxial Growth and Structural Properties of RF Magnetron Sputtered Germanium Buffer Layer on Silicon

“…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]. However, the explosive GeH 4 gas is injected as a reaction gas in the CVD system to fabricate Ge films.…”