Abstract
We have deposited Ge, SiGe, SiGeSn, AlAs, GaAs, InGaP and InGaAs based structures in the same metalorganic vapor phase epitaxy (MOVPE) growth chamber, in order to study the effect of the cross influence between groups IV and III-V elements on the growth rate, background doping and morphology. It is shown that by adopting an innovative design of the MOVPE growth chamber and proper growth condition, the IV elements growth rate penalization due to As “carry over” can be eliminated and the background doping level in both IV and III-V semiconductors can be drastically reduced. In the temperature range 748–888 K, Ge and SiGe morphologies do not degrade when the semiconductors are grown in a III-V-contaminated MOVPE growth chamber. Critical morphology aspects have been identified for SiGeSn and III-Vs, when the MOVPE deposition takes place, respectively, in a As or Sn-contaminated MOVPE growth chamber. III-Vs morphologies are influenced by substrate type and orientation. The results are promising in view of the monolithic integration of group-IV with III-V compounds in multi-junction solar cells.
Highlights
There is considerable interest in exploiting band gap engineering possibilities offered by the integration of III-V and IV-based materials for optoelectronic and for photovoltaic applications [1,2,3]
It can be pointed out that few IV-based material coating runs are enough to obtain high growth rate, as compared with the values reported in literature, related to samples grown at similar temperatures and precursor partial pressure
Growth chamber, during SiGeSn deposition a considerable amount of arsenic can be released from the metal organic vapor phase epitaxy (MOVPE) reactor walls and be incorporated in SiGeSn and subsequent layers, (ii) the As contamination can be reduced during the deposition by growing the group IV compounds at high growth rate, around 100 nm/min, while it remains at level around 1019 cm−3 when the growth rate is one order of magnitude lower (10 nm/min)
Summary
There is considerable interest in exploiting band gap engineering possibilities offered by the integration of III-V and IV-based materials for optoelectronic and for photovoltaic applications [1,2,3]. 2. Materials and Methods is feasible, with promising perspectives for the realization of high efficiency, low cost, The III-V and group IV-based semiconductor deposition has been carried out by multi-junction solar cell structures. The reactor modifications means of a AIX 2800G4 MOVPE “planetary” system (from AIXTRON SE, Herzogenrath, concerned: (i) the use of a special triple gas injector with a bigger dimeter than standard, Germany), whose growth chamber has been preliminarily modified in order to reduce for enhancing the precursor utilization efficiency and reducing the parasitic deposithe cross doping between groups IV and III-V elements. In order to reduce the unwanted doping in IV (III-V)-based semiconductors, after the last III-V (IV) deposition, we have applied the growth procedure of depositing on the graphite elements of the MOVPE growth chamber several “coating runs” constituted of IV (III-V) elements materials. The graphite ring, usually operating at lower temperature than the other growth chamber parts, has not been replaced
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