Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

MBE Growth of Self-Assembled InAs and InGaAs Quantum Dots Embedded in
Silicon Matrix
strained Si layer, with in-plane strain gradient up to 0.5 % along growth direction,
and out-of-plane GPA strain up to 10 % found to be only near the surface,
which results in a strong tetragonal distortion of the coherent InAs epitaxial
layer. However, this sample showed a weak optical emission at 1153 nm and
it was discussed as defect related transition. The wavelength of the observed
peak does not match with direct band gap InAs optical transition. However, the
temperature dependence measurement (Fig. 5.24(b)) conrmed that the observed
peak was not observed at a temperature above 14 K. Fig. 5.24(a) shows the PL
power dependence of this transition. All spectra reveal transverse optical (TO)
phonon-assisted exciton emission of the Si substrate and barrier at energy of 1.1
eV, which is equivalent to a wavelength of ∼ 1127 nm.
The indirected emission increased with the excitation power till the saturation.
However, due to the weak connement an additional small thermal energy may let
Figure 5.24: Photoluminescence (PL) measurement of 1 ML InAs QDs embedded in
silicon matrix grown on 5 ◦ o-cut (100) substrate. (a) PL power dependence measurement
at 8 K. (b) PL temperature dependence measurement at an excitation power of
10 W/cm 2 .
the electrons to escape from the connement zone, therefore the optical emission
for this structure was not detected above a temperature of 15 K.
90