以有機金屬氣相沈積法側向磊晶成長氮化鎵晶體之特性研究

Abstract

三五族氮化合物的磊晶成長研究由來已久，其優點在於可以有各種不同比例的三元及四元化合物，可以調整能隙寬度、晶格常數及折射率等，故在光電元件及高速元件的應用有相當的潛力，在短波長方光二極體及雷射二極體都有不錯的表現，並有達到量產程度的元件開發出來。 但其缺點在於基板價格昂貴，造價偏高，且因基板為氧化鋁，和成長的磊晶膜有晶格不匹配的問題，而在1997年底，日亞化學公司推出壽命長達一萬小時的藍光雷射二極體，其秘訣便在於降低磊晶膜的缺陷密度，故基板的特性將嚴重影響磊晶膜的品質。 本研究以選擇性成長(Selective Epitaxial Growth: SEG)的技術為出發點，利用有機金屬氣相沈積法，作側向磊晶成長(Epitaxial Lateral Overgrowth: ELO)的研究，希望能利用側向成長時，隔絕磊晶層和基板因晶格常數不同，所造成的缺陷的延伸，以期能在較便宜的基板(如矽基板)上，成長出高品質、低缺陷密度的三五族化合物磊晶層。在經由強酸溶液腐蝕ELO基板後，可以利用原子力顯微鏡(Atomic Force Microscope: AFM)觀察到三種不同的蝕刻點。本研究也探討了一些側向磊晶成長的機制。

Investigating the epitaxial growth of III-V nitride compound semiconductor is lengthy. The advantages of the III-V nitride compound semiconductor are that the energy gap, lattice and the reflective index are tunable. Furthermore, the III-V nitride compound semiconductor can be a good material for fabricating short wavelength and high-speed devices. III-V nitride based LED has already been mass-produced. Although, III-V nitride compound semiconductors have numerous advantages, the main issue is that no suitable substrate exists for epitaxial growth. Nichia Chemical Industries announced the fabrication of blue laser diode, with a long lifetime of over 10000 hours, in late 1997. The main objective of employing blue laser diode is to reduce the defect density of the epitaxial layer. The epitaxial lateral overgrowth (ELO) method is used to improve film quality. This study starts from the technique of selective epitaxial growth (SEG) and uses metal-organic chemical vapor deposition (MOCVD) epitaxial growth to grow the substrate. Three kinds of etch pits on an ELOG substrate are formed by wet chemical etching and observed by an atomic force microscope (AFM). Meanwhile, the growth mechanism of ELOG is another important topic.