Low-temperature semiconductor bonding method for manufacturing high-efficiency five-junction solar cell

Abstract

The invention relates to a low-temperature semiconductor bonding method for manufacturing a high-efficiency five-junction solar cell. The method is characterized by firstly, growing epitaxial layers which have different band gaps and have matched lattices on GaAs and InP substrates; and then, connecting the two groups of epitaxial layers in series through a low temperature semiconductor bonding method to form a 5-junction solar cell. In a bonding technology, firstly, the bonded epitaxial layers are globally planarized by using a chemical mechanical polishing process, then a highly doped film on a bonding surface is cleaned with ammonia water, and then a bonding surface chemical bond is activated by using a low-energy plasma, and the bonding of the epitaxial layers is achieved within 30 minto 150 min. The method has advantages that a restriction problem of lattice mismatch to high-quality epitaxial layer growth is solved, which is good for increasing the yield of a multi-junction cell;and low temperature bonding is adopted, process time is short, a bonding process does not affect the photoelectric performance of the epitaxial layer, process complexity and cost are reduced, and commercialized production is easy to realize.

Description

technical field [0001] The invention belongs to the technical field of physical power sources, and in particular relates to a low-temperature semiconductor bonding method for preparing high-efficiency five-junction solar cells. Background technique [0002] At present, the photoelectric conversion efficiency of commercialized GaInP / Ga(In)As / Ge triple-junction solar cells is 30% (AM0), which is close to the limit of the expected efficiency of this type of cell structure, and there is little room for further improvement. In the past 10 years, due to the technical bottleneck of lattice-mismatched epitaxial growth of 4-junction III-V solar cells, the increase in cell efficiency and yield has been lower than expected, and the manufacturing cost is high. These multi-junction cells are difficult to meet the needs of future space vehicles. The American Spectrum Laboratory reported that a 5-junction III-V solar cell was developed by bonding technology, and its photoelectric conversi...

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Problems solved by technology

A large number of studies have confirmed that the graded buffer layer cannot completely suppress the threading dislocations formed during the lattice mismatch epitaxy process, because the growth of the above-mentioned high Al content material itself is easy to introduce deep level defects of Al-O, and the threading dislocations The existence of defects further increases the difficulty of suppressing deep-level defects, and it is difficult to prepare high-quality epitaxial layers; second, InP substrates have poor mechanical strength, long-term high-temperature growth, and stress accumulated due to lattice mismatch It will cause warping or even cracking of the InP wafer; thirdly, during the MOCVD epitaxy process, some reaction gases or products and substrate fixing brackets can easily cause pollution and damage to the back of the substrate, and continue the epitaxy process on such a back, Can have a great impact on the quality of growing material

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