| Summary: | 碩士 === 國立成功大學 === 物理研究所 === 81 === The band gaps and Fermi level positions of a series of InAlAs
ternary alloy compounds were studies at room temperature by
photoreflectance (PR) spectroscopy. The PR spectra so-called
Franz-Keldshy oscillations which is directed related to a high
constant electric field in top layer of the special designed
structure, which consist of a micron of high doping buffer
layer and a thousand of undoped layer. Thus surface barrier
height and Fermi level pinning can be evaluated. Our
experiments demonstrated that when the aluminum concentration
is varied from 0.42 to 0.57, the Fermi level is not pined at
the midgap, as is commonly believed, but instead varies almost
linearly from 0.42 to 0.63eV below the conduction band edge. In
addition, it was found that the unpinning surface can be
obtained by a proper chemical etching processign.
|
|---|
