In-situ study of pn-heterojunction interface states in organic thin film transistors

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• 作者：Rongbin Ye ; Koji Ohta ; Mamoru Baba
• 关键词：Organic thin film transistor ; Field-effect mobility ; Threshold voltage ; pn-Heterojunction
• 刊名：Thin Solid Films
• 出版年：3 March, 2014
• 年：2014
• 卷：554
• 期：Complete
• 页码：137-140
• 全文大小：573 K

文摘

In this paper, we have investigated the density of pn-heterojunction interface states by evaluating the threshold voltage shift with in-situ measurement of electrical characteristics of a sandwich fluorinated copper phthalocyanine/pentacene thin film transistor with various thicknesses of pentacene thin films. A threshold voltage (V_T) undergoes a significant shift from + 20.6 to + 0.53 V with increasing the thickness of pentacene. When the thickness of pentacene is more than a critical thickness of 15 nm, V_T undergoes hardly any shift. On the other hand, the value of mobility is lightly decreased with increasing the thickness of pentacene due to the effect of the bulk current. Thus the V_T shift is attributed to the increase of drain current in the sandwich device. In order to explain the V_T shift, a model was assumed in the linear region of thin film transistor operation and the V_T shift agrees with a tan^鈭?#xA0;1 function of film thickness. The total charge density (Q₀) of 1.53 脳 10^鈭?#xA0;7 C/cm² (9.56 脳 10¹¹ electrons or holes/cm²) was obtained. Furthermore, the V_T shift and Q₀ could be adjusted by selecting a p-type semiconductor.