電區熔生長矽及矽鍺合金之晶粒發展與界面型態觀察研究

Abstract

晶體結構的發展對於太陽能多晶矽的光電性質是影響的關鍵，尤其是晶界的種類。本篇論文為了研究晶體結構的發展，以不同遷移速度(2-6 mm/min)下進行細晶片的電區熔長晶。並發現在低遷移速度時，<111>方向為主導晶向，在高遷移速度時<112>方向為主導晶向。其中，大部分的non-∑晶界傾向沿著溫梯方向生長，但有少數會沿著降低界面能的方向生長。換言之，除了高遷移速度之外，斜的∑3晶界因晶粒競爭的關係而減少。若晶粒均被∑晶界分開，其競爭情況可看成晶界間的互相作用，兩個∑3n晶界行成的晶界也為∑3n晶界，會遵守特定的關係。換言之，當∑晶界碰到non-∑晶界，而non-∑晶界會被保留下來，這也解釋了在低遷移速度時∑晶界會逐漸減少。 最近，Nakajima提出具有為小的阻成分布的多晶矽鍺來當作新的光電材料，吾人也以不同鍺摻雜濃度(0-12.46 at.%)下進行細晶片的電區熔長晶。並發現在低遷移速度時，<111>方向仍為主導晶向

The evolution of grain structures, especially the types of grain boundaries (GBs), during directional solidification is crucial to the electrical properties of multicrystalline silicon used for solar cells. To study this, the electric molten zone crystallization (EMZC) of silicon wafers at different drift speeds from 2 to 6 mm/min was considered. It was found that <111> orientation was dominant at the lower drift velocity, while <112> orientation at the higher drift velocity. Most of the non-∑GBs tended to aligned with the thermal gradient, but some tilted toward the unfavorable grains having higher interfacial energies. On the other hand, the tilted ∑3 GBs tended to decrease during grain competition, except at the higher speed, where the twin nucleation became frequent. The competition of grains separated by ∑GBs could be viewed as the interactions of GBs that two coherent ∑3n GBs turned into one ∑3n GB following certain relations as reported before. On the other hand, when ∑ GBs met non-∑ GBs, non-∑ GBs remained which explained the decrease of ∑ GBs at the lower speed. Nakajima et al. has recently proposed multicrystalline SiGe with microscopic compositional distribution as a novel annual photovoltaic material. We also studyed the evolution of grain structures of multicrystalline SiGe at different Ge concentration from 0 to 12.45 at. % was considered. It was found that <111> orientation still was dominant at high Ge concentration. Nakajima et al. has recently proposed multicrystalline SiGe with microscopic compositional distribution as a novel annual photovoltaic material. We also studyed the evolution of grain structures of multicrystalline SiGe at different Ge concentration from 0 to 12.45 at. % was considered. It was found that <111> orientation still was dominant at high Ge concentration.