Gas-phase deposited thin-film silicon emitters for solar cells: high quality homoepitaxy at 325°C

The authors demonstrate high-quality homoepitaxial growth of thin P doped emitter layers by electron cyclotron resonance chemical vapor deposition (ECR-CVD) on (100)-oriented crystalline silicon at T=325°C. It is shown that epitaxial growth sets in when the gas-phase doping concentration PH₃/SiH₄ exceeds 1500 ppm. From secondary ion mass spectroscopy analysis and electron spin resonance methods, it is concluded that in spite of the low processing temperature, P dopants diffuse about 100 nm deep into the wafer thereby moving the pn-junction away from the interface. Solar cells have been prepared with conversion efficiencies as high as 14%. This demonstrates the technological potential of the simple processing technique used here