利用雷射剝離與晶圓黏合技術製作氮化鎵雷射共振腔劈裂鏡面

Abstract

本論文將氮化鎵雷射二極體結構轉移到砷化鎵和矽基板上，利用劈裂技術獲得高平整的的劈裂面和高反射率的鏡面。首先，利用氫化物氣相磊晶法(HVPE)在藍寶石基板(Al2O3)上製備氮化鎵雷射二極體結構，再利用感應耦合電漿蝕刻(ICP)定義出氮化鎵雷射二極體的條狀圖案。接下來利用晶圓黏合技術將雷射二極體結構黏合在薄的砷化鎵或矽基板上。經由利用不同的黏合金屬和實驗溫度以及壓應力試驗過，再用雷射剝離技術將藍寶石基板給移除。雷射二極體結構也順利轉移至砷化鎵和矽基板上。因為砷化鎵和矽基板是屬於立方晶體，劈裂後具有完美的解理面。所以將砷化鎵雷射二極體結構黏合在這些立方晶體的基板上，再劈裂後會讓附在上面的砷化鎵雷射結構劈裂面獲得很好的平整度，以致得到極高的雷射共振腔反射鏡面。我們也利用原子力顯微鏡(AFM)對這些劈裂後的雷射二極體反射鏡面做分析。量測結果得到低於3nm的表面粗糙度(rms roughness)，由理論分析可得到反射係數超過95%的雷射共振腔劈裂面。

Smoothly cleaved facets with high reflectivities have been demonstrated on GaN laser diodes after the devices were transferred onto GaAs substrates. The GaN based laser diode structure was first fabricated by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates. Inductively coupled plasma (ICP) etch was applied to define GaN laser stripe patterns. The samples were then mounted onto thin GaAs substrates using wafer-bonding technology. Various types of bonding metals, bonding pressures, and bonding temperatures have been attempted in the process. Laser lift-off (LLO) technique was applied to remove the original sapphire substrate and hence transfer the GaN based laser diodes structure onto GaAs substrates. Since the cubic substrates have well-defined cleaved facet, the GaN based laser diodes structures bonded onto the substrates also formed smooth facets after cleavage. The cleaved facets of GaN laser diodes have been characterized using atomic force microscopy (AFM) with less than 3 nm roughness. Theoretical calculations indicated that a rms roughness of less than 4 nm is required to obtain the reflectivity of greater than 90% for the laser cavity. The present study demonstrated the feasibility of transferring GaN laser structures onto other more appealing substrates for formation of laser cavities.