氮化鎵相關材料之磊晶成長與特性分析

Abstract

在本研究中，我們以自行組裝的有機金屬汽相磊晶法成長六角結構及立方結構的氮化鎵薄膜。對於薄膜的特性分析，則是採用X光繞射、霍爾量測、激發光譜及拉曼散射，另外還採用了拉曼散射的空間相關模型來分析非對稱的拉曼散射模。 論文研究之初期，我們對於在藍寶石基板上所成長的氮化鎵薄膜磊晶參數進行最佳化，這些磊晶參數包括緩衝層的厚度、磊晶溫度、五族與三族的汽相比例、基板氮化過程以及載流氣體中氮氣與氫氣的比例等。之後，我們也對於在砷化鎵(001)基板上成長立方晶形的氮化鎵薄膜進行磊晶溫度的研究，在這研究中發現六角晶形及立方晶形結構同時存在於氮化鎵薄膜中。 對於砷原子摻雜於氮化鎵薄膜的研究方面，我們在製備氮化鎵薄膜的過程中，在不同的磊晶溫度將TBA (tertiarybutylarsine)以不同的流量引入反應腔體中。我們發現在攝氏900到1000度之間，微量砷摻雜的氮化鎵薄膜的品質較未摻雜的薄膜品質高。而在攝氏700到800度之間，我們得到了含砷量達約0.7%的薄膜。對於砷原子在氮化鎵薄膜中擴散的效應研究，我們嘗試對含有砷化鎵中間層的三明治結構進行熱退火處理，發現與砷相關的550nm的綠光激發光譜會隨著熱退火溫度升高而出現，但是當退火溫度增加至1000 oC時，由於溫度過高，導致綠光光譜的消失。

We have grown the hexagonal and cubic GaN by using our homemade atmospheric metalorganic vapor phase epitaxy system (AP-MOVPE). The characteristics of these samples were investigated by using X-ray measurements, Hall measurements, photoluminescence, and Raman scattering. The spatial correlation modal of Raman scattering was adopted to analyze the asymmetric broadening of Raman modes. At the beginning, we tried to optimize the growth parameters of undoped GaN on sapphire, such as, buffer layer thickness, growth temperature, V/III ratio, nitridation, N2/H2 carrier gas mixing ratio, etc. For the cubic GaN growth, we tried to grow GaN on GaAs (001) substrate at different temperature. We found co-existing of hexagonal and cubic phase in the samples. To investigate the As incorporation effect in GaN, we introduced the TBA (tertiarybutylarsnie) into the reactor when preparing GaN samples at different growth temperature or different flow rate. The lightly As-doped GaN grown at the temperature of 900oC~1000oC showed better quality than undoped GaN. At 700oC~800oC, we obtained GaAsxN1-x with As content of ~0.7%. For the study of As diffusion effect in GaN, we tried to anneal the GaN samples with thin GaAs interlayer. The intensity of characteristic green-line emission around 500 nm in the PL spectra increased with annealing temperature. However, the green emission disappeared because the annealing temperature of 1000 oC was too high.