| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 101 === In this research, we use the electron cyclotron resonance chemical vapor deposition (ECR-CVD) to deposit high-crystallinity germanium thin films on single crystal silicon substrate, and investigate the structural properties of the films. Because of the higher carrier mobility and the lower energy bandgap compared with Si, Ge is widely used for near infrared optical communication devices. Moreover, for the lattice constant of Ge matches that of GaAs, a common material for high efficiency III-V solar cell, crystal Ge is also used as the substrate of this kind of solar cell. However, the cost of crystal Ge is about 4 times higher than that of crystal Si, so in order to lower the cost, many researches have been doing efforts to grow high quality epitaxial Ge films on Si substrates to replace the crystal Ge substrates. Traditional methods to grow Ge on Si heteroepitaxy are usually at high substrate temperature (> 600℃), here, we present a new way to grow the Ge epilayers under low substrate temperature (180℃).
In this work, we use optical emission spectroscopy (OES) to monitor the plasma distribution when processing. The structural properties are measured and analyzed by spectroscopy ellipsometry (SE), Raman Spectrometer, and X-ray diffractometer (XRD), and atomic force microscopy (AFM). Without annealing, we can obtain a high-crystallinity structure in a 40-nm film with the full width at half maximum of Ge (400) XRD rocking curve of 4119 arcsec, and an 1.44-nm root mean square surface roughness in a 90-nm film.
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