非等向性陽極化所生成之多孔質矽的製程及特性研究

Abstract

我們利用Hydrazium在(100)矽晶片上作出V字形的圖案,然後在電解液 HF 加酒精的溶液中進行陽極化反應以生成多孔質矽.結果可得到:當(100) 與(111)平面同時存在時,多孔質矽有選擇性的生成在(111)的平面上.且在 完全相同的電解液濃度,電流密度及作用時間下,(100)面上的光致發光頻 率高於(111)平面.由電流-電壓特性可知欲在(111)平面生成多孔質矽所需 的電壓低於(100).由光熱偏折光譜可決定當電解液濃度下降時,其對應的 能量有向高能偏移的趨勢. Recently,it is found during our experiment that porous silicon layer grows preferentially on the (100) over (111) Si surface. The process consists of two steps. First,hydrazine is used to etch V-grooves on (100) Si wafer. Second,the (111) walls of etched V-grooves are selectively anodized in HF/ethanol solution to form PSL. The anodization step takes place at a smaller bias voltage for (111) than (100). Under the same conditions of electrolyte concentration,current density and the duration for anodization,the frequency is higher for the measured PL from (100) than (111). From the current-voltage measurement,we conclude that the formation of PSL on (100) occurs at higher energy. We are also able to induce a blueshift in the PL of PSL by controlling the HF concentration at a lower level from the results of the photothermal deflection spectroscopy experiment.