T. Yodo et al., RELATIONSHIP BETWEEN THE OPTICAL AND STRUCTURAL-PROPERTIES IN GAAS HETEROEPITAXIAL LAYERS GROWN ON SI SUBSTRATES, Journal of crystal growth, 141(3-4), 1994, pp. 331-342
The relationship between the optical and structural properties in GaAs
/Si heteroepitaxial layers (heteroepilayers) grown by molecular beam e
pitaxy with various buffer layers (GaAs, AlAs, GaAs/AlAs superlattice
(SL), and GaAs/Si SL with layer thickness of 10-50 nm) at the interfac
e between the GaAs and Si are examined using photoluminescence (PL) sp
ectroscopy, double-crystal X-ray diffraction, and transmission electro
n microscopy (TEM). In as-grown samples, the use of various buffer lay
ers grown at low temperatures improves the crystalline quality and red
uces the density of non-radiative centers. The optimum annealing tempe
rature for improving the crystalline quality of GaAs/Si heteroepilayer
s, regardless of whether a buffer layer was used during growth, is bet
ween 950 and 1000-degrees-C as determined by PL intensities, full widt
h at half-maximum of X-ray rocking curves, and threading-dislocation d
ensity. In contrast, annealing at temperatures higher than 900-degrees
-C for GaAs/Si heteroepilayers with SL buffer layers degrades the surf
ace morphology and does not improve either the optical or structural p
roperties, because annealing damages the SL structures. The crystallin
e quality of a 1 mum thick GaAs heteroepilayer without a buffer layer
or with a GaAs buffer layer is drastically improved by ex-situ anneali
ng at temperatures higher than 950-degrees-C. The threading-dislocatio
n density decreases from values on the order of 10(11)-10(12) cm-2 in
the as-grown state to values on the order of 10(6)-10(7) cm-2 near the
surface.