聚酰亚胺LB膜MIS结构C－V特性

C- V CHARACTERISTICS OF MIS STRUCTURES WITH LANGMURI-BLODGETT POLYIMIDE FILMS

本文报道了Ａｌ／ＬＢ聚酰亚胺膜／Ｐ－Ｓｉ（１００）ＭＩＳ结构的Ｃ一Ｖ特性研究结果．６７层ＬＢ膜样品Ｃ－Ｖ特性近乎理想，具有负的固定电荷密度约１０１１ｃｍ－２量级，平带时滞后小于０．３Ｖ对于ＭＩＳ隧道结，除了在－０．５—－１．５Ｖ间具有反型层箝位产生的电容峰外，在－１．５—－４Ｖ间还出现了另一电容峰值．假设在强电场下隧穿能力剧增，从而结构由隧穿限制区重新进入半导体限制区，可以解释这一峰值的出现，考虑到少子注入引入的扩散电容，正。

C-V technology is an effective method of studing semiconductor interfaCe. This paper will rePort some interesting new results of C-V characteristics which are obtained from MIS tunnel junction with LB insulting films.The substrates used in present research are p-type (100) silicon wafers which were doped at the concentrstion of 1015 cm-3. The insultators are LB polyimide films and the circular aluminium top electrodes wereevaporated through a metal mask in a vacuum system. In the case of thicker LB films, the trap density is low on the interface of polyimidel silicon so that a quasi-ideal C-V characteristics with a hysteresis about 0.26v is obtained. On the contrary, in the case of thiner LB films, the interface trap density is high so the curve deviates obviously from the ideal situation. Based on the rang6s of sweeping voltage, we can regard the serious hysteresis as the result that carriers inject into the traps of LB films at large bias voltage.For MIS tunnel junction, besides the hump produced by the invertion layer clamping between-0.5 and -1.5V, Wb have found another hump between -1.5 and -4V. It may be introduced by the change of the junction from tunnel limited to semiconductor limited regime again. Because when the tunnel probability increases immensely at strong electrical field, the insultor will be completely'transparent to carriers and theMIS structure will change into Li he- Metal- Semiconductor (LMS) junction. The second hump does not appear in some' samples. It is possible that if there are many defects on the insultor, the MIS structure will change. into LMS junction just at lower voltage.Under large negative bias, minority carriers will inject into silicon through LB films. If the capacitance introduCed by minority carriers injection is taken into account, the difference of hUmps between voltage sweeping forward and back can be well explained.(Correspondent:LIN Hal’all3 Department ofElectronlcEngineenng,SoutheastUniversity,NalljingZ10018)