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

MBE Growth of Self-Assembled InAs and InGaAs Quantum Dots Embedded in
Silicon Matrix
optimization of silicon surface preparation recipes, have led to a controlled formation
of QDs on a at silicon substrate. Moreover, the MBE growth of n-type
arsenic (As) doped silicon layers with a controlled doping prole as a preparation
phase for the realization of P-N junctions will be also presented in this chapter,
hence this chapter deals with all the growth aspects related to silicon matrix
optimization with III/V QDs.
In this contribution, the focus is on the basic growth studies addressing mainly
morphological and structural properties of quantum dots like structures grown
directly on silicon surfaces, with a main emphasis on surface preparation and
growth parameters.
5.2 Experimental Details
All samples for the initial study and optimization were grown by a GEN II MBE
system on exactly oriented n-type (100) silicon all gures, except Fig. 5.2(b),
which was grown on (111) Si substrate orientation. The silicon substrate surfaces
were ex-situ cleaned using buered HF (NH 4 /HF : H 2 O) (1:1) for 4 minutes
as a pre-removal step of the surface native silicon dioxide (SiO 2 ) followed by an
in-situ thermal atomic hydrogen (AH) assisted surface cleaning process at 500 ◦ C
(45 minutes with P H = 3.7×10 −7 T orr) in the buer chamber. The nal thermal
oxide desorption was done in the growth chamber within the temperature range
of 700 − 900 ◦ C. The quality of the surface preparation and the dots formation
process are monitored in-situ by reection high energy diraction. Additional improvement
for the cleaning and growth was achieved by exposing the Si surface to
low Ga ux (0.1 ML/s) (Fig. 5.3). Dierent growth parameters such as (growth
temperature, V/III ratio, In growth rate and InAs coverage) on structural properties
of InAs QDs without buer layer (Sec. 5.3.2) and after depositing a 50 nm
silicon buer layer (Sec. 5.3.3) were investigated.
5.3 Results and Discussion
This section presents the results of the epitaxial nucleation and growth optimization
of InAs quantum dots and dashes on silicon substrates.
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