Integration of GaAs on Ge/Si towers by MOVPE (original) (raw)
Related papers
Selective epitaxial growth of GaAs on Ge by MOCVD
Journal of Crystal Growth, 2006
We have selectively grown thin epitaxial GaAs films on Ge substrates with the aid of a 200 nm thin SiO 2 mask layer. The selectively grown structures have lateral sizes ranging from 1 µm width up to large areas of 1 by 1 mm 2 . The growth with the standard growth procedure for GaAs growth on Ge substrates reveals a limited amount of GaAs nucleation on the mask area and strong loading effects caused by diffusion of group III precursors over the mask area and in the gas phase. Reduction of the growth pressure inhibits GaAs nucleation on the mask area and reduces the loading effects strongly, but favors the creation of anti phase domains in the GaAs. An optimized growth procedure was developed, consisting of a 13 nm thin nucleation layer grown at high pressure, followed by low pressure growth of GaAs. This optimized growth procedure inhibits the nucleation of GaAs on the mask area and is a good compromise between reduction of loading effects and inhibition of anti phase domain growth in the GaAs. X-ray diffraction and photoluminescence measurements demonstrate the good microscopic characteristics of the selectively grown layers.
Selective Epitaxial Growth of GaAs on Ge Substrates with a SiO2 Pattern
2007
We have selectively grown thin epitaxial GaAs films on Ge substrates with the aid of a 200 nm thin SiO2 mask layer. The selectively grown structures have lateral sizes ranging from 1 um width up to large areas of 1 by 1 mm2. The growth is fully selective, thanks to an optimized growth procedure, consisting of a 13 nm thin nucleation layer grown at high pressure, followed by low pressure growth of GaAs. This growth procedure inhibits the nucleation of GaAs on the mask area and is a good compromise between reduction of loading effects and inhibition of anti phase domain growth in the GaAs. Nevertheless, both microscopic and macroscopic loading effects can still be observed on x-section SEM images and profilometer measurements. X-ray diffraction and low temperature photoluminescence measurements demonstrate the good microscopic characteristics of the selectively grown GaAs.
Structural investigation of MOVPE-grown GaAs on Ge by x-ray techniques
The selection of appropriate characterization methodologies is vital for analyzing and comprehending the sources of defects and their influence on the properties of heteroepitaxially grown III-V layers. In this work, we investigate the structural properties of GaAs layers grown by metal-organic vapour phase epitaxy on Ge substrates-(1 0 0) with 6 • offset towards 1 1 1 -under various growth conditions. Synchrotron x-ray topography is employed to investigate the nature of extended linear defects formed in GaAs epilayers. Other x-ray techniques, such as reciprocal space mapping and triple axis ω-scans of (0 0 l)-reflections (l = 2, 4, 6), are used to quantify the degree of relaxation and presence of antiphase domains (APDs) in the GaAs crystals. The surface roughness is found to be closely related to the size of APDs formed at the GaAs/Ge heterointerface, as confirmed by x-ray diffraction (XRD), as well as atomic force microscopy and transmission electron microscopy.
Nanoscale Growth of GaAs on Patterned Si(111) Substrates by Molecular Beam Epitaxy
High-quality and defect-free GaAs were successfully grown via molecular beam epitaxy on silicon dioxide patterned Si(111) substrates by a two-step growth technique. Compared with the one-step approach, the two-step growth scheme has been found to be a better pathway to obtain a superior-quality GaAs on Si. Taking advantages of low energy for both Si(111) surface and GaAs/Si(111) interface, the two-step grown GaAs of total 175 nm atop patterned Si(111) substrates exhibits atomically smooth surface morphology, single crystallininty and a remarkably low defect density. A low-temperature GaAs nucleation layer of the two-step growth helps relieve the misfit stress by accommodating the misfit dislocations at the very adjacent GaAs/Si interface. The excellent properties of the two-step grown GaAs were investigated and verified by field-emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Finally we demonstrated a GaAs on Si solar cell, which could represent an important milestone for future applications in light-emitting diodes, lasers, and photodetectors on Si.
OMVPE growth of undoped and Si-doped GaAs epitaxial layers on Ge
1998
Low-pressure organometallic vapor-phase epitaxial (LP-OMVPE) growth of undoped and Si-doped GaAs on Ge was carried out with a variation in growth temperature and growth rate. In the case of undoped and Si-doped GaAs, etch patterns showed that the epilayers consist of a single domain. Double crystal X-ray diffraction (DCXRD) indicated the compressive GaAs and the full-width at half-maxima for Si-doped GaAs decreased with increasing growth temperature. The 4.2 K photoluminescence (PL) spectrum of the undoped GaAs showed an acceptor bound excitonic peak (AX transition) at 1.5125 eV and the Si-doped GaAs showed two hole transitions of Si acceptors at 1.4864 eV along with the excitonic peak at 1.507 eV. This indicated the absence of Ge related peaks, i.e., (e-Ge) transitions. The electrochemical capacitance voltage profiler showed that the Si-doping efficiency for GaAs on Ge was less than that in GaAs on GaAs. The profiler revealed an npn structure in both the cases where the p region was in GaAs. The secondary ion mass spectroscopy (SIMS) results qualitatively indicated the absence of outdiffusion of Ge into GaAs.
The European Physical Journal Applied Physics, 2020
We investigate the influences of GaAs buffer layer (bl) growth parameters such as temperature and thickness on the structural, morphological, crystalline and optical quality of metal organic vapor phase epitaxy (MOVPE) grown heterostructures of GaAs on Ge. It has been found that the optimal bl conditions significantly decrease the effects of anti-phase boundaries (APBs) even it was grown on offcut Ge substrate by two-step growth technique with AsH3 pre-flow to promote double atomic step formation. It is shown that while the growth temperature increases the growth rate of the GaAs bl, it reduces the crystalline quality when it exceeds the critical temperature of 535 C. Similar behavior has been considered for the thickness of the bl around 25 nm and it results in low full width at half maximum (FWHM) value, high photoluminescence peak intensity and high internal quantum efficiency (IQE).
Materials Research Bulletin, 2000
GaAs/Ge heterostructures were grown under different growth conditions by low-pressure metal organic vapor phase epitaxy (LP-MOVPE) and investigated by transmission electron microscopy (TEM). Abrupt heterointerface and antiphase domain (APD)-free single domain GaAs epilayers on Ge substrates were achieved under specific growth conditions. The lattice indexing of high-resolution transmission electron microscopy (HRTEM) exhibited excellent lattice line matching between the GaAs epilayer and the Ge substrate. These results led us to conclude that the optimal growth parameters for achieving high-quality GaAs/Ge heterostructure are As/Ga ratio of ϳ88:1, growth rate of ϳ3 m/h, and growth temperature of 675°C.
Multi-technique characterisation of MOVPE-grown GaAs on Si
Microelectronic Engineering, 2011
The heterogeneous integration of III-V materials on a Si CMOS platform offers tremendous prospects for future high speed and low power logic applications. That said this integration generates immense scientific and technological challenges. In this work multi-technique characterisation is used to investigate properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Si substrates -(100) with 4: offset towards <110> -under various growth conditions. This being a crucial first step towards the production of III-V template layers with a relatively lower density of defects for selective epitaxial overgrowth of device quality material. The optical and structural properties of heteroepitaxial GaAs are first investigated by micro-Raman spectroscopy and photoluminescence and reflectance measurements. High-resolution X-ray diffraction (HR-XRD) is used to investigate structural properties. Advanced XRD techniques, including double-axis diffraction and X-ray crystallographic mapping are used to evaluate degrees of relaxation and distribution of the grain orientations in the epilayers, respectively. Results obtained from the different methodologies are compared in an attempt to understand growth kinetics of the materials system. The GaAs overlayer grown with annealing at 735:C following As predeposition at 500:C shows the best crystallinity. Close inspection confirms the growth of epitaxial GaAs preferentially oriented along (100) embedded in a highly-textured polycrystalline structure.