氮化銦鎵以及磷化銦鎵鋁的高亮度發光二極體之量測分析及研究

Abstract

目前高亮度發光二極體再世界各地蓬勃發展，其中氮化銦鎵以及磷化銦鎵鋁是兩種目前業界最熱門的材料，住要是因為它們兩個共有的特性：出光效率好。其中氮化銦鎵的多量子井結構，隨著銦的含量不同，可以做出波長由藍光到綠光的發光二極體，同樣的磷化銦鎵鋁，則是可以隨著各種原子含量調配的不同，做出波長由綠光到紅光的發光二極體。在本篇論文中，氮化銦鎵的多量子井結構，和磷化銦鎵鋁的薄膜和多量子井結構成功的由有機金屬化學沈積系統合成。在結構上由X光繞射譜線及拉曼光譜分析，掃瞄式電子顯微鏡則顯示磷化銦鎵鋁的薄膜樣品表面的生長狀況，高解析度穿透式電子顯微鏡影像則能顯示出氮化銦鎵的多量子井結構包括其量子井生長的厚度。 在氮化銦鎵的多量子井的部份，在本篇文章中比較了兩片結構差不多，但是銦含量不同的兩片樣品。我們做了一系列光激發光的量測，像是變溫度的光激發光，改變激發光強度的光激發光，以及量測它發光的生命週期，藉以得到不同的量對於發光機制及物理特性的影響。並經由拉曼和高解析度X光繞射譜來分析樣品內部的材料結構以及長的好壞。 磷化銦鎵鋁的薄膜的部份，我們由掃瞄式電子顯微鏡抓出了兩片樣品，其中一片長的相當平整，另外一片則是不太均勻的薄膜。我們分析了一系列雙異質結構樣品的變溫光激發光和光反射來比較放光和吸收隨溫度變話的情行。並且也做了拉曼和高解析度X光繞射譜來分析樣品內部的材料結構以及長的好壞。

Recently High Brightness Light-Emitting Diode (HBLED) has been widely used and investigated. Nowadays GaN/InGaN and InGaAlP are the two most popular materials to made such a HBLED, just because the high efficiency [1]. For InGaN multiple quantum well (MQW), we get two 5QWs samples. The barrier and well width are almost the same (it can be proven by Transmission electron microscopy (TEM)), but the In composition of the InGaN quantum well is quite different. A series of PL measurement such as temperature dependent PL, power dependent PL, Time-resolved Photoluminescence (TRPL) are measured. In order to discus the peaks shift, quantum-confined Stark effect (QCSE), and localization effect of In-rich sample. X-ray diffraction (XRD) and Raman scattering also show us the sample’s quality. For InGaAlP, we will first discuss the composition and the film quality to realize the characterization of InGaAlP thin films will be performed. And about the thin films, two series of (AlxGa1-x)0.5In0.5P films were grown on lattice-matched GaAs by low pressure MetalOrganic chemical vapor deposition under different conditions and studied by scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL), photoreflectance (PR), X-ray diffraction (XRD), and Raman scattering. SEM shows the surface uniformity, EDX can calculate the composition of each atom. Comparative PL and PR measurements and analyses indicated the emission properties and the absorption properties. The degree of variations in compositions and film quality with the growth conditions were found from the spectral analyses. Raman spectral and XRD features are more sensitive to the sample growth parameter variations [2]. AlGaInP Material The quaternary alloy (AlxGa1-x)0.5In0.5P, lattice-matched to GaAs and with a direct band-gap transition in the green-red light wavelength range, is an important material in visible light emitting diodes (LEDs) [3,4], laser diodes [5,6], heterojunction bipolar transistors (HBT) [7], matrix for the growth of self-assembled quantum dots (QDs) [8] and devices for 630-700 nm wavelength range applications such as laser pointers, barcode readers, digital versatile disk (DVD) players [9] and solid-state lighting [10]. Metalorganic chemical vapor deposition (MOCVD) technology has been widely employed for the growth and industry production of this quaternary and related materials [4, 5, 8, 9]. Atomic ordering may occur under certain conditions during the epitaxial growth of AlGaInP by MOCVD, which forms a Cu-Pt ordered structure, i.e. the group-III In, Ga and Al atoms spontaneously segregate into alternating {111} monolayers during growth rather than forming a disordered alloy with the In, Ga and Al atoms randomly distributed on all the group III sublattices [10,11]. This ordering results in the reduction of alloy bandgap and the negative effects in the subsequently grown devices. It is important to control and optimize the growth conditions to avoid or depress the appearance of ordering and other types of defects, to acquire high quality InGaAlP layers [2, 12].