在近十年中，過渡金屬二硫族化物 (Transition metal dichalcogenides,
TMDs) 因其多樣的電學特性被廣泛研究。由於單層的 TMDs 具有直接能
隙而獲得對光偵測的高靈敏度，使其被廣泛應用於光偵測元件中。在本
論文中，我們製作一個複合光偵測器，其結構為在 WS2 通道旁製作梳狀
的 WS2/WSe2 異質結構作為與金屬的接觸。在光的照射下，由於 WS2 與
WSe2 的異質接面屬於 Type-II 能帶結構，因此在梳狀結構上產生大量的
光激發電子從 WSe2 轉移到 WS2。電荷的轉移導致接觸能障下降，使得
金半接觸變好，進而讓元件效能提升。文中所製作的複合光偵測器其載子
遷移率可達 8.9 cm2
/V ·s 及 107 的電流開關比，而光響應可以到達 4800
A/W。此外，我們也對梳狀異質結構進行了 TLM 量測。在不照光時，接
觸電阻為 106.7 kΩ · µm 而轉移長度為 33.64 nm；在照光後，接觸電阻降
至 10.49 kΩ · µm 而轉移長度降為 3.56 nm。

In the past decade, transition metal dichalcogenide(TMDs) have been extensively studied due to their diverse electronic properties. Because of the
high sensitivity to light detection obtained from the direct band gap properties, monolayer TMDs have been widely used in optoelectronic devices.
In this work, we demonstrate a composite photodetector comprising WS2
channel sandwiched between strip-shaped WS2/WSe2 heterostructure as the
metal contact. Upon light illumination, since the type-II band alignment at
the WS2/WSe2 heterojunction, a large number of photoexcited electrons are
generated on the strip structure and transferred from WSe2 to WS2. Charge
transfer leads to reduce contact barrier and makes contact better, thereby
improving the performance of the device. The composite photodetector
exhibits a high mobility of 8.9 cm2
/V ·s and a current on/off ratio of 107
.
It also can reach a high responsivity of 4800 A/W. Furthermore, transfer
length method(TLM) measurement was also performed on strip-shaped heterostructure. The contact resistance is 106.7 kΩ · µm and the transfer length
is 33.64 nm without illumination. Yet, under light illumination, the contact
resistance decreases to 10.49 kΩ · µm and the transfer length reaches 3.56
nm.

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