以電漿輔助式分子束磊晶成長氮化鎵奈米柱及其在光伏上的應用

Abstract

本論文利用電漿輔助式分子束磊晶系統在矽基板上成長異質結構的氮化鎵奈米柱材料並且應用在太陽能光伏電池上。 依照場發射掃描式電子顯微鏡的結果從矽基板至長出氮化鎵奈米柱的過程，我們藉此說明材料的成長機制，接著再分別依照不同成長基板溫度和不同鎵流量了解磊晶結果的差異，從場發射掃描式電子顯微鏡和反射高能電子繞射發現Ⅴ/Ⅲ原子流量比由小到大和成長基板溫度由低至高會造成類似的氮化鎵材料之表面形貌變化。X-ray 繞射說明成長基板溫度提高有利於材料結晶性，從光激螢光光譜得知較細的氮化鎵奈米柱，藍位移現象會更加明確。就反射率可得知在成長基板溫度800oC、鎵流量最小時會有明顯抗反射的效果。 最後我們會將不同製程參數的試片做成元件，用原子層沉積成長二氧化錫作為導電材料，接著會鍍上鋁和金電極形成鋁（Al）/p型矽/氮化鎵奈米柱/二氧化錫（SnO2）/金（Au）的太陽能電池架構，並量測其效率。

In this thesis, the heterostructure GaN nanorods material was grown on Si substrate by Plasma-Assisted Molecular Beam Epitaxy （PA-MBE）and fabricated to solar cells. According to the results of Field Emission Scanning Electron Microscopy（FE-SEM）, we can explain the growth mechanism of GaN nanorods on Si (111). For different growth temperatures and different gallium flow rate, we can also observe various GaN epitaxial processes. By the analysis of FE-SEM and Reflection High Energy Electron Diffraction（RHEED）, we can find the similar trends of surface morphology between the ratio of Ⅴ/Ⅲ from low to high and the growth temperature from low to high. X-ray diffraction shows the substrate temperature increase beneficial to the crystalline of GaN material. From the photoluminescence spectrum, the blue shift phenomenon became more clear for smaller size of GaN nanorods. Reflectivity shows that there will be significant anti-reflective effect at the condition of the growth substrate temperature at 800oC and the lowest gallium flow rate. Finally, we made the samples with different growth parameters into devices, which are deposited Tin oxide（SnO2）as the conductive material, then coated with aluminum and gold electrodes. Solar cells were fabricated in the structure as Al/p-Si/GaN nanorods/SnO2/Au, and were measured their efficiency.