一維奈米結構氮化銦光電特性研究

Abstract

本論文中研究氮化銦一維結構尺度上光學、電性與光電導的效應。使用有機金屬化學沈積技術成長具有單晶烏采結構氮化銦奈米結構。接著製作單根氮化銦奈米元件。光學量測中，20K下氮化銦發光位置約為0.84 eV。溫度由20K到100K時光致發光位置開始有異常藍移的現象接著升至室溫時由於一般的能隙收縮造成紅移。此一光致發光機制為能帶與能階間復合機制與電子在表面上累積有關。氮化銦一維奈米結構的高載子濃度(2.7x1019 1.65x1020 cm-3)可由傅立葉轉換紅外光譜儀證實。在電性量測上，所有單根氮化銦奈米元件的導電率在50到8000 -1cm-1之間。變溫電導量測中顯示其具有類金屬的傳輸特性。光電導量測中對其尺寸的影響，我們發現其最大的光電流反應可以達到1000 A/W，這是氮化銦中第一次被發現的現象。當氮化銦奈米帶的直徑改變由60至230 nm，光電流有非常明顯的增加。由於一維結構的尺寸效應形成明顯的表面電子累積造成較短的載子生命期和較低的載子移動率，使得光電流對尺寸有明顯的效應。

We have studied optical, transport, and photoelectric properties on dimensionality of one-dimensional (1D) nanostructure of InN. Single-crystalline InN nanobelts with wurtize structure have been synthesized using metalorganic chemical vapor deposition (MOCVD). The fabrication of single nanobelt device has been also demonstrated. For optical measurement, we found that the photoluminescence (PL) peak position of the samples is observed at around 0.84 eV at 20 K. In addition, the PL peak position reveals anomalous blueshift as temperature increases from 20K to 100K and then follows redshift from 100K to 300K due to normal bandgap shrinkage. The PL emission mechanism in InN nanobelts can be explained by the combination of the model of free-to-bound recombination and electron surface accumulation. The high carrier concentration of InN nanobelts in the range of 2.7x1019 1.65x1020 cm-3 has been further manifested by the study of plasma edge absorption in the Fourier Transform Infrared (FTIR) examination. For electrical measurement, the overall conductivity of the nanobelts is in the range of 50 8000 -1cm-1. The temperature dependence of dark conductivity has indicated the metallic transport behavior of the single InN nanobelt. Size-dependent hotoconductivity (PC) has been observed on the InN nanobelts and the maximal photocurrent responsivity reaching to 1000 A/W has been demonstrated for the first time. It is found that the responsivity has increased significantly as nanobelt size increases from 60 to 230 nm. The size-effect on the PC performance could be explained by the electron surface accumulation in the size-confined 1D nanostructure of InN giving rise to shorter lifetime and lower mobility of carrier.