Improving the Quality of Epitaxial Foils Produced Using a Porous Silicon-based Layer Transfer Process for High-Efficiency Thin-Film Crystalline Silicon Solar Cells

Kerfless layer-transfer of thin epitaxial silicon foils using novel multiple layer porous silicon stacks with near 100% detachment yield and large minority carrier diffusion lengths

“…in HP-DL). The reorganization characteristics of our porous silicon double layers have already been explained in [10]. In porous silicon double layers, the LP-TL acts as a vacancy supply layer and increases the porosity of the HP-DL during the annealing process, because of the vacancy concentration gradient between the two layers.…”

“…1 and explained in Section 1. The methodology for the preparation of samples for lifetime measurement has already been detailed in [10,13]. Here, a recapitulation with additional details is provided.…”

“…Firstly, a stack of porous silicon is electrochemically-etched on the surface of a highly boron-doped wafer in a HF-based electrolyte. The standard porous silicon stack used today is a double layer of 250-300 nm-thick high porosity detachment layer (HP-DL) underneath a 1-2 mm-thick low porosity template layer (LP-TL) [8][9][10]. After etching, the sample is annealed at a high temperature ( Z1100 1C) in hydrogen ambient [4,9,10], which results in the sintering of porous silicon leading to the formation of a detachment plane in the HP-DL and a well-closed LP-TL surface suitable for the following in-situ epitaxial growth of silicon.…”

“…The standard porous silicon stack used today is a double layer of 250-300 nm-thick high porosity detachment layer (HP-DL) underneath a 1-2 mm-thick low porosity template layer (LP-TL) [8][9][10]. After etching, the sample is annealed at a high temperature ( Z1100 1C) in hydrogen ambient [4,9,10], which results in the sintering of porous silicon leading to the formation of a detachment plane in the HP-DL and a well-closed LP-TL surface suitable for the following in-situ epitaxial growth of silicon. Note that the detachment layer (DL) and the template layer (TL) have also been called as the separation layer and starting layer, respectively, in literature [8,11].…”

In situ annealing and high-rate silicon epitaxy on porous silicon by mesoplasma process

“…22,23) It can also be understood, as has been reported in the reference, that porous Si reorganization occurs through vacancy diffusion processes driven by a vacancy concentration gradient between the pore (or voids) and its surrounding lattice. 5) However, unlike the conventional process that forms a smooth surface free of open voids, 6,24) the porous Si after Ar-H 2 mesoplasma annealing shows a rough surface with large voids, as shown in Fig. 1(d).…”