Influence of the process parameters on the morphological and electronic properties of liquid phase crystallized silicon films on glass

摘要

The crystallization of thin silicon films directly on glass with a material quality comparable to commercially available multi crystalline silicon wafers is one of the major goals in thin film technology. In the past the resulting poly crystalline silicon layers fabricated using the solid phase crystallization SPC method suffered from a number of shortcomings such as small grains and a high defect concentration which limited the achievable open circuit voltage to values below 500 mV. We were able to overcome those limitations with liquid phase crystallization LPC utilizing a continuous wave diode laser or an electron beam. LPC results in poly Si on glass with randomly oriented grains up to cm in length and mm in width with a very low amount of intra grain defects. In this work we show how an improved crystallization process in terms of the scanning velocity of the laser, pre heating of the specimens and the applied laser intensity leads to a changing morphology of the resulting poly Si layers. Using a well defined parameter set, we are able to substantially decrease the amount of high angle boundaries which are known from literature to reduce the overall electronic quality and to trigger a preferential surface orientation of 100 . First a Si H c Si hetero junction cells fabricated using this advanced crystallization process showed a benefit in open circuit voltage