Effect of Acceleration Voltage on Phosphorus-Implanted Emitter of p-Type Crystalline Silicon Solar Cell

Abstract

In this study, the effect of acceleration voltage on emitter properties was investigated. Phosphorus ion was implanted into a silicon substrate at acceleration voltages of 7, 13, and 20 KeV. As the acceleration voltage increased, the amorphous layer thickness increased from 14 to 33 nm. The projected ranges were around 10 to 13 nm, and little change was observed with the acceleration voltage. The as-implanted phosphorus concentrations as well as the junction depth were higher for higher acceleration voltages. As the phosphorus acceleration voltage increased, a larger and rougher area of contrast was observed at the amorphous/crystalline interface. After thermal treatment at 750 degrees C, strains were observed by high-resolution X-ray diffraction for all acceleration conditions. It was observed that a higher acceleration voltage resulted in a higher intensity of rocking curves with more fringes. Sheet resistances decreased rapidly after thermal treatment above 850 degrees C. The sheet resistance decreased with increasing annealing temperature, while at every temperature, the sample at 7 KeV acceleration voltage showed a higher sheet resistance than the samples at 13 and 20 KeV. The mobility increased for temperatures up to 850 degrees C but the carrier concentrations showed little change. Above 850 degrees C, the mobility did not show much change, but the carrier concentration increased. It is considered that the dopant activation was highly affected by the carrier concentration and not by the mobility.