On conductivity type conversion of p-type silicon exposed to a low-frequency inductively coupled plasma of Ar + H2

The treatment of an Ar + H2 plasma generated by a low-frequency inductively coupled plasma system at 500 degree C introduces an n-type region (of average electron concentration ~1015 cm-3) on a Czochralski p-type substrate, forming a deep p--n junction. Examination by an electron microscope shows that the plasma treatment produces uniform nanocones on the surface and some defects, such as dislocations and platelets, in the subsurface. All these observed results are hydrogen-related. The conductivity type conversion is due to the formation of hydrogen-enhanced oxygen-related thermal donors (OTDs) as well as hydrogen-incorporated shallow thermal donors. The OTD-related signals are directly observed in the infrared absorption spectra. Both donors are annihilated after annealing at 550 degree C for 10 min, resulting in conductivity recovery from n-type to original p-type. The electrical properties of the as-formed junction are investigated using current versus voltage (I--V), capacitance versus voltage (C--V) and Hall effect measurements. On this basis, the junction depth, carrier profile and hydrogen diffusion behaviour are studied. Moreover, a clear photovoltaic effect of the junction has been observed through the Suns-Voc and illuminated I--V tests.