Controlled Doping Methods for Radial p/n Junctions in Silicon

P/n and n/p junctions with depths of 200 nm to several micrometers have been created in flat silicon substrates as well as on 3D microstructures by means of a variety of methods, including solid source dotation (SSD), low‐pressure chemical vapor deposition (LPCVD), atmospheric pressure chemical vapor deposition, and plasma‐enhanced chemical vapor deposition. Radial junctions in Si micropillars are inspected by optical and scanning electron micro­scopies, using a CrO 3 ‐based staining solution, which enables visualization of the junction depth. When applying identical‐doping parameters to flat substrates, ball grooving, followed by staining and optical microscopy, yields similar junction depth values as high‐resolution scanning electron microscopy imaging on stained cross‐sections and secondary ion mass spectrometry depth profilometry. For the investigated 3D microstructures, doping based on SSD and LPCVD give uniform and conformal junctions. Junctions made with SSD‐boron doping and CVD‐phosphorus doping could be accurately predicted with a model based on Fick's diffusion law. 3D‐microstructured silicon pillar arrays show an increased efficiency for sunlight capturing. The functionality of micropillar arrays with radial junctions is evidenced by improved short‐circuit current densities and photovoltaic efficiencies compared with flat surfaces, for both n‐ and p‐type wafers (average pillar arrays efficiencies of 9.4% and 11%, respectively, compared with 8.3% and 6.4% for the flat samples).

Перевод пока недоступен