Study of p-type laser doping using ALD AlOx as a dopant source

• Published in: 2014 IEEE 40th Photovoltaic Specialist Conference (PVSC) pp. 3032 - 3035
• Main Authors: Bo Xiao, Ly Mai, Dong Lin, Hallam, Brett, Chee Mun Chong, Lennon, Alison, Wenham, Stuart
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2014
• Subjects: AlO x; Boron; charge carrier lifetime; Doping; Laser applications; laser doping; Photovoltaic cells; Silicon; Silicon compounds
• ISSN: 0160-8371
• DOI: 10.1109/PVSC.2014.6925573

The formation of heavily doped p + region on p-type silicon substrates using laser doping through a layer of ALD AlO x is studied. A 532 nm continuous wave (CW) laser is used to incorporate Al atoms from the AlO x layers to form p + silicon. The p + regions formed through laser doping are found to be affected by various parameters such as laser speed and power. Sheet resistances as low as 10 Ω/□ were achieved using a power of 15 W and laser scanning speed of 0.5 m/s. The impact of the laser doping process on effective minority carrier lifetime is investigated using only the AlO x layer as a dopant source, as well as with the addition of a Boron dopant source. Laser doping boron have better protection by introducing a lifetime drop from 67 μs to 57.7 μs after laser doping comparing to the lifetime drop of laser doping AlO x from 62.5 μs to 46.1 μs. However, the addition of a boron spin on dopant source may induce voids in the laser doped region.