The effect of a-GaAs/a-Si double buffer layers on GaAs-on-Si as determined by transmission electron microscopy

Abstract

A high-quality GaAs epilayer was successfully grown on a Si substrate using a-GaAs/a-Si double buffers, which were crystallized by thermal cyclic annealing. Double crystal x-ray diffraction measurements showed that the full width at half maximum of the rocking curve for the GaAs epilayer was only 102 arcs. The effect of a-GaAs/a-Si double buffers was examined in detail by transmission electron microscopy. Transmission electron microscopy characterizations revealed obvious bending behaviour of dislocations in the a-GaAs/a-Si buffered epilayer. Most threading dislocations and planar defects were confined within the crystallized double buffers. The dislocation density was reduced to 2.6 × 10 6 cm −2 at a thickness of 1.0 µm in the first epitaxial layer and was further improved to under 1.3 × 10 6 cm −2 in the second epitaxial layer. Transmission electron microscopy observation and analysis revealed a defect reduction mechanism.

Heteroepitaxial growth of GaAs on Si by MOVPE using a-GaAs/a-Si double-buffer layers

“…8(a), the pits were counted according to the sizes and the results were listed in the right top of the same figure. As was reported elsewhere, there were much more dislocations and therefore more complicated dislocation behaviors in the a-GaAs/a-Si buffered GaAs-on-Si specimens, such as the bending or interactions of dislocations observed by transmission electron microscopy (TEM) [22]. As a result, it is possibly to cause a variation in the dislocation numbers along the epilayer thickness.…”

Growth mechanism of an aluminium-induced solid phase epitaxial (AI-SPE) Si0.5Ge0.5layer using in situ heating transmission electron microscopy

“…1,2 In addition, the epitaxial silicon-germanium (epi-SiGe) film can serve as a template for high-performance multi-junction solar cells due to a tunable energy band gap that is a function of the Ge fraction. [3][4][5] Conventionally, the epi-SiGe film can be grown using chemical vapor deposition (CVD), 6 or molecular beam epitaxy (MBE); 7 however, these techniques usually require strict conditions of high vacuum, high temperature, and use of toxic precursors. It was reported that the epi-SiGe film can be fabricated using an Al solid phase epitaxial (AI-SPE) process from a-Ge/Al layers on a Si substrate after annealing at 300 °C.…”

Defect Reduction in GaAs/Si Films with the a-Si Buffer Layer Grown by Metalorganic Chemical Vapor Deposition

“…Thus no lattice mismatch strain is present at the GaAs/Si interface, and dislocations are unnecessary in the GaAs layer, although dislocations and planar defects can occur in the a-Si layer. [24,25] By introduction of a thin a-Si layer on the surface of Si wafers, the dislocation density in GaAs/Si epilayers was reduced effectively. [24−27] Hao et al obtained 2.2-µm GaAs/Si epilayers through use of a 15-Å a-Si layer as buffer layer, and GaAs/AlGaAs quantum well lasers were achieved on silicon.…”

“…[24−27] Hao et al obtained 2.2-µm GaAs/Si epilayers through use of a 15-Å a-Si layer as buffer layer, and GaAs/AlGaAs quantum well lasers were achieved on silicon. [26,27] Insertion of a 20-Å a-Si layer before the two-step growth process, Uen et al [24,25] achieved 4-µm GaAs/Si epilayers with an etch-pit density close to 1 × 10 6 cm −2 .…”

“…The dislocation density in the sample of GaAs/Si epilayers can be reduced by about two orders of magnitude by using the a-Si buffer layer, 088101-3 and is lower than those reported previously. [24,25] To further reveal the effect of the a-Si buffer layer on GaAs/Si epilayers, dislocations in the sample with the a-Si layer are observed directly by cross-sectional high-resolution TEM (XHRTEM). Figure 5(a) shows the XHRTEM of the GaAs/Si interface along the [011] zone axis.…”