利用電漿輔助式分子束磊晶成長氮化矽／氮化鎵薄膜並觀察其特性分析

Abstract

本論文利用電漿輔助式分子束磊晶系統在藍寶石基板上成功地成長出氮化鎵、氮化矽薄膜。利用光激螢光光譜、掃描式電子顯微鏡及X射線光電子能譜分析其物理特性。 利用低溫氮化鎵緩衝層生長以及控制基板溫度和氮/鎵比例提高在藍寶石基板上磊晶之氮化鎵晶體品質。發現當基板溫度為760°C以及高度氮富含地條件下，氮化鎵形成六角形貌的奈米柱。其低溫光激螢光光譜半高寬為18毫電子伏特。由金屬有機化學氣相沈積的氮化鎵基板上成長出氮化鎵薄膜對比，低溫光激螢光光譜半高寬為7毫電子伏特且無氮或鎵空缺所導致的缺陷發光，證明氮化鎵晶體品質較佳。並由原子力顯微鏡成長40奈米氮化鎵薄膜的表面粗糙度為1.92奈米。X射線光電子能譜分析氮化矽薄膜只存在單一的Si2p(Si3N4)的化學鍵，並推測其成長速度至少為0.82奈米/小時。藉由原子力顯微鏡分析,氮化矽薄膜可以改善富氮條件下成長氮化鎵表面粗糙的形貌。在高電子遷移率電晶體的應用中可以減少由於表面粗糙所產生的表面態，進而改善其電學特性。

In this dissertation, the gallium nitride and silicon nitride grown on c-plane sapphire substrate by plasma assisted molecular beam epitaxy (MBE) were studied. The photoluminescence (PL), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the physical properties. The quality of GaN nano-rods can be improved by using low temperature GaN buffer layer and the control of N/Ga flux ratio and growth temperature. Under the highly N-rich condition, the GaN nano-rods formed a hexagonal shape at 760°C. The low temperature PL measurement showed that the full width at half maximum (FWHM) of the near band edge emission was 18 meV. On the other hand, the GaN formed thin film structure on GaN substrate which grown by Metal-organic Chemical Vapor Deposition (MOCVD). The low temperature PL spectra showed that the near band edge emission peak FWHM is 7 meV and without deep level emission, which can prove the quality of GaN has been greatly improved. The roughness of GaN film was 1.92 nm which observed by Atomic Force Microscope (AFM). XPS energy showed there was only Si-N bonding in the SiN and the growth rate was 0.82 nm/hour at least. The SiN can decrease the roughness of N-rich GaN. During the high electron mobility transistors (HEMTs) application, it will reduce the relaxation, cracking, and surface roughness of the top layer. That leads to devices with improved characteristics.