Electrical characteristics of amorphous Si:H/crystalline Si0.3Ge0.7 heterojunction solar cells grown on compositionally graded buffer layers

Oshima, Ryuji; Yamanaka, Mitsuyuki; Kawanami, Hajime; Sakata, Isao; Matsubara, Koji; Sugaya, Takeyoshi

doi:10.1016/j.jcrysgro.2015.03.054

Cited by 2 publications

(1 citation statement)

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“…[23][24][25][26][27][28][29][30][31][32] In particular, since higher optical adsorption of Ge than amorphous-(a-) and µc-Si:H can be realized in longer wavelength region, higher conversion efficiency can be expected by combining highly crystallized Si:H and Ge:H layers with tandem structure solar cells. [33][34][35][36][37][38][39] However, one of the main concerns is the significant difference in bond length in the crystalline phase, and according to the lattice constant of c-Ge and c-Si, the lattice mismatch is 4%. In addition, for the film growth at low temperatures below ∼250 °C, the crystallinity of Si films in the early stages of film growth on µc-Ge films and the subsequent crystalline grain growth with the progress of Si film deposition are still major concerns.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature formation of crystalline Si:H/Ge:H heterostructures by plasma-enhanced CVD in combination with Ni-nanodots seeding nucleation

Lu¹,

Makihara²,

Takeuchi³

et al. 2017

Jpn. J. Appl. Phys.

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Hydrogenated microcrystalline (µc) Si/Ge heterostructures were prepared on quartz substrates by plasma-enhanced chemical vapor deposition (CVD) from VHF inductively coupled plasma of SiH4 just after GeH4 employing Ni nanodots (NDs) as seeds for crystalline nucleation. The crystallinity of the films and the progress of grain growth were characterized by Raman scattering spectroscopy and atomic force microscopy (AFM), respectively. When the Ge films were grown on Ni-NDs at 250 °C, the growth of µc-Ge films with crystallinity as high as 80% was realized without an amorphous phase near the Ge film/quartz substrate interface. After the subsequent Si film deposition at 250 °C, fine grains were formed in the early stages of film growth on µc-Ge films with compositional mixing (µc-Si0.85Ge0.15:H) caused by the release of large lattice mismatch between c-Si and c-Ge. With further increase in Si:H film thickness, the formation of large grain structures accompanied by fine grains was promoted. These results suggest that crystalline Si/Ge heterojunctions can be used for efficient carrier collection in solar cell application.

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