有機垂直型三極體研究

The study of organic vertical-type triode

鄭孝信(Shiau-Shin Cheng)

指導教授 ： 吳孟奇博士 ； 朱治偉博士

國立清華大學/電機資訊學院/電子工程研究所/博士(2011年)

https://doi.org/10.6843/NTHU.2011.00690

摘要

在本文中我們將探討有機垂直型電晶體的操作機制和其應用。有機垂直型電晶體是由兩個背對背的蕭特基二極體所組成，並且可行性地架構在可撓塑膠或是玻璃基板上。由於元件的通道長度是由主動層厚度所決定，所以通道長度可以控制到次微米並且當元件施加不同基極偏壓時，飽和區的輸出電流具有調製效果。為了計算出元件的有效遷移率，在元件高電壓中的電流電壓圖將採用空間電荷限定電流模型來定義之。有機垂直型電晶體不但具有和有機薄膜電晶體一樣的電壓操作模式，並且也同時有和雙極面電晶體一樣的電流驅動模式。所以，我們透過一顆有機垂直型電晶體串聯電阻來實現第一顆負載電阻式的反向器並且探討其轉換曲線特性。在電性改善方面，為了避免在金半介面產生電偶極，在金半介面中採用氧化鉬當作緩衝層。當元件採用氧化鉬及鋁當作射極電極時，其特性相對於以金、銀當作射極電極有明顯改善，推測原因在於有緩衝層的保護下，金屬不容易擴散到有機半導體層並且可以降低能障。元件在基極電壓為-5V時，輸出電流可以到達-16.1 μA並且電流開關比為103。為了更進一步實行互補式反向器，相同特性的p和n通道有機垂直型電晶體是必要的。所以當兩個元件很匹配時(p通道元件的開電流為-229 μA，關電流為-67.6 nA，抵補電壓為-0.8 V; n通道元件的開電流為377 μA，關電流為86.9 nA，抵補電壓為0.4 V;)，在輸出電壓為4V時電流增益大約為9。另一方面，元件以電流方式驅動，元件採用階梯式能階時可以獲得很高的電流增益。因為載子透過階梯式能階來增加其能量，可以避免在基極電極產生複合電流而增加輸電流。所以此時元件的傳輸因子可以到達0.99並且電流增益為20.93。當元件有較高的電流增益時，第一顆有機電流鏡可以被實行，而其輸出輸入電流比為0.75,而輸出電阻為105歐姆。而這些應用將有助於在積體電路上的發展。

關鍵字

有機垂直型三極體 ； 電流開關比 ； 反向器 ； 傳輸因子 ； 電流增益 ； 電流鏡

並列摘要

In this thesis, we have investigated the fundamental property of organic vertical-type triodes (OVTs) and their application. The OVTs are promising fabricated by employing two back-to-back Schottky diodes on the flexible or glass substrate. Due to the channel length depending on the thickness of active layer, the channel length can be controlled down to sub-micrometer and the device exhibits modulations with apparent saturation region while applying various supply voltages to the base electrode. To calculate effective mobility of the device, it is investigated by fitting the current-voltage characteristics at high voltages to the space-charge limited current (SCLC) model. The OVTs feature not only the operation procedures similar to those of bipolar junction transistors, but also those of planar-type organic thin-film transistors. Therefore, the first organic resistor-load inverter can also be achieved by integrating an OVT with a load resistor and their voltage transfer curves are demonstrated. To avoid the formation of the dipole at the metal/organic junction, a buffer layer of molybdic oxide (MoO3) is inserted at the metal/organic junction of OVT. The performance of devices featuring MoO3/Al as the emitter electrode is enhanced relative to that of corresponding devices with Au and Ag, presumably because of the reduced in the contact barrier and the prevention of metal diffusion into the organic layer. The device exhibited an output current of -16.1 μA at VB = -5 V and a current ON/OFF ratio of 103. To further realizing the complementary inverter, the similar performance of the p-channel OVT (ON current: -229 μA; OFF current: -67.6 nA; turn-on voltage: -0.8 V) and n-channel OVT (ON current: 377 μA; OFF current: 86.9 nA; turn-on voltage: 0.4 V) is fabricated and it exhibits a voltage gain of ca. 9 at a low supply voltage of 4 V. While the OVTs are operated under the current-driving mode, the OVTs operated at pronounced saturation with high gain by incorporating cascade-type energy band structure have been fabricated. Due to the most injection carriers can gain higher energy through the stepwise energy level, more carriers can surmount thin metal base electrode and diffused into the collector layer. Therefore, the device exhibited the transport factor of 0.99 and current gain of 20.93. Since the device exhibits the enough large current gain, a current mirror operated at out/in current ratio of 0.75 and output resistance of 105 Ω was achieved by integrating two p-channel OVTs with a load resistor. Theses application can enhance the development of the integrated circuits.

並列關鍵字

organic vertical-type triode ； current on/off ratio ； inverter ； transport factor ； current gain ； current mirror

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