具穿隧結構氮化鎵奈米線白光二極體之研製

Abstract

本論文主要探討氮化鎵奈米結構之製作與特性分析，分成兩個部分論述。第一部份細述以V-L-S機制成長氮化鎵奈米結構，第二部份是氮化鎵奈米線發光二極體之製作與量測。 首先，本文敘述實驗室自製V-L-S氮化鎵奈米線晶體成長系統，並且使用SEM、PL、EDS、TEM、XPS等量測技術，分析氮化鎵奈米線晶體之外觀、品質及晶體之成分。從PL結果得知晶體激發出中心位置在363 nm，半高全寬為42 nm的紫外光，與一寬頻的黃光發光。由EDS和XPS元素分析中得知晶體的主要成分為氮化鎵，而由TEM材料分析得知晶體為單晶結構。 吾人以此奈米線晶體結構製作發光二極體元件，並量測其電壓-電流特性、電激發光頻譜以及光電流。元件展現出非一般理想發光二極體的特性。在正負偏壓下皆有可見光及紫外光發光，且發光頻譜有強烈藍移現象。並於文末提出光助穿隧模型嘗試解釋此奈米線發光二極體之電激發光機制。

In this thesis, we present the growth, analyzing, fabrication, and characterization of gallium nitride (GaN) nanowires light emitting devices. The growth of GaN nanowires structures was conducted in a home-built vapor-liquid-solid (V-L-S) system. The following spectroscopic instrument of scanning electron microscopy (SEM), photoluminescence (PL), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscope (XPS) were used to characterize the morphology, composition, and crystalline properties of the GaN nano-structures grown by the V-L-S method. From the PL analysis pumped by a 266nm Nd:YAG solid-state laser, we observed a peak emission wavelength at 363nm with a full width at half maximum (FWHM) of 42nm, and a wideband yellow emission. From the EDS and XPS data analysis we identify the material’s composition to be binary GaN. Data from the TEM analysis suggest the GaN nanowires grown by the V-L-S method to be single crystalline. Light-emitting devices base upon the V-L-S-grown GaN nanowires were further fabricated and characterized. From the current-voltage, electroluminescence (EL), and photocurrent measurements, these devices exhibit non-ideal electrical characteristic. The devices emit ultraviolet and visible light under both bias polarities, and are observed a large spectral blue shift as the injection current increased. Finally, we give a photo-assisted tunneling model to explain the EL mechanism of this device.