多重晶面銦氮化鎵/氮化鎵微米柱和奈米柱光電元件

Abstract

本論文建構高銦含量三維結構多晶面銦氮化鎵/氮化鎵微米柱和奈米柱發光元件。首先向下蝕刻氮化鎵基板形成氮化鎵微米柱(奈米柱)，接著用金氧化學氣相沉積成長法形成多晶面銦氮化鎵/氮化鎵微米柱(奈米柱)。 在建構多重晶面微米柱過程中，首先於氮化鎵微米柱上成長出六方晶系非極性{112 ̅0}和半極性{112 ̅2}晶面，接著漸變成長為非極性{101 ̅0}和半極性{101 ̅1}晶面。這種晶面消長的現象是來自於成長過程中不同晶面有不同成長速率彼此競爭的結果。銦氮化鎵/氮化鎵多重量子井成長於多晶面微米柱上亦延續此晶面消長的結果而產生電激發寬頻譜，該多重晶面微米柱發光二極體能夠在無螢光粉幫助下電激發產生從460奈米至660奈米全可見光頻譜之白光。半極性與非極性面解決了極性面的量子效應，而增進發光效率。 在此論文中亦證明了奈米金字塔頂奈米柱綠光發光二極體及光伏元件。高銦含量多重量子井成長於半極性奈米金字塔和非極性奈米柱表面，奈米柱表面可容許高銦含量成長故可製造出電激發綠光元件以及寬太陽能吸收頻譜，奈米柱結構可增加有效多重量子井面積以及光子收集效率。在模擬器照射下一太陽環境中，金字塔頂奈米柱光伏元件有短路電流1.16 mA/cm2，開路電壓0.68 V，量子效率58% 和能量轉換效率 0.38%。

Fabrication of high In content three-dimension multi-facet microrod and nanopillar optoelectronics are demonstrated in this dissertation. The microrods and nanorods were fabricated by top-down patterned etched from GaN template, followed by metal organic chemical vapor deposition epitaxial regrowth. For multi-facet microrod LED, hexagonal nonpolar {112 ̅0} and semipolar {112 ̅2} facets were first formed on the microrods, then gradually transformed to nonpolar {101 ̅0} and semipolar {101 ̅1} facets. This facet evolution was attributed to the growth competition among different crystal planes. The multiple quantum wells (MQWs) grown on the microrods also followed this facet evolution and resulted in broad emission spectrum. The device can have direct white light emission covering full visible spectral range from 460 nm to 660 nm under electrical injection. Semipolar and nonpolar facets enhance the optical emission efficiency significantly. We also used patterned top-down etch to fabricate GaN nanorod from a c-plane GaN template and a subsequent regrowth to fabricate pyramid-on-pillar nanostructure. High In content InGaN/GaN MQWs were grown on the pyramid and pillar facets, followed by a conformal p-GaN layer growth. Electrical contacts were fabricated on the LED sample by standard chip fabrication process. The conformal growth and properties of InGaN/GaN MQWs were studied by high resolution transmission electron microscopy (HR-TEM). Cathodoluminescent (CL) and photoluminescent (PL) measurements were used to study the quantum emission efficiency and carrier recombination dynamics. The electroluminescence (EL) and the photovoltaic measurement of the fabricated nanostructure optoelectronic device was demonstrated and showed promising potential for high In content InGaN/GaN MQW applications.