磷化銦奈米線場效電晶體之光電特性

Abstract

本實驗使用溶液-液相-固相成長機制製備，平均直徑20奈米的磷化銦奈米線，並利用電子束微影技術，製作多組兩點量測之奈米線元件。我們將元件放置於低溫致冷器內，在變溫環境下(300℃到120℃)量測元件的電流電壓特性。此奈米線元件之電阻隨著溫度降低而升高，呈現半導體的特性，且不論電阻高低，在室溫時電流電壓曲線皆為線性關係。為分辨元件電性是來自半導體奈米線或金屬與奈米線間接觸點，我們以熱活化傳輸理論擬合元件的電阻對溫度曲線，觀察到室溫電阻愈小的元件，較符合熱活化傳輸理論。我們推測低電阻元件的電性主要來自於磷化銦奈米線，而是溫電阻愈高的元件，其電性主要來自於金屬電極與奈米線間接觸點的貢獻。此外我們使用基板為閘極電極，在室溫測量到磷化銦奈米線場效電晶體元件的電性，結果顯示此磷化銦奈米線為自然n型半導體。更進一步，我們使用綠光雷射照射在磷化銦奈米線元件探討光電性質，發現以接觸點電阻為主的奈米線元件，其光電流比暗電流增加率達百分之百，比較以奈米線為主要貢獻為的元件還要高，雖然奈米線為主的元件照光時能產生較大的光電流。

Indium phosphide (InP) nanowires with an average diameter of 20 nm were grown for the fabrication of two-probe devices by using the standard electron-beam lithography technique. Current-voltage (I-V) behaviors of the nanowire devices were measured at temperatures from 300℃ down to 120℃. The resistance of the nanowire devices increases with decreasing temperatures, implying the semiconducting behavior in the nanowires. The electron transport as well as the temperature dependent resistance R(T) was calculated. We found that, for the devices having low room-temperature resistance, the R(T) agrees well with the thermal activated transport theory. The low resistance devices might give the intrinsic electrical poperties of the InP nanowires. On the other hand, the high resistance devices could be used to study the electrical properties from the nanocontact. Additionally, the back gate technique was adopted to check the field-effect properties. Electrical characterization on the InP nanowire field-effect transistors indicates that the InP nanowires are natively n-type semiconductors. Moreover, the optoelectronic properties of the two-probe nanowire devices were explored under the exposure of the green light laser (532 nm). We found that the photocurrent, in comparison with the dark current, enhances with a ratio up to 100% for the contact dominated devices while the excited photocurrent is still smaller than that in the nanowire dominated devices.