Nitride Semiconductor Laser End Face Protection Against Oxygen Diffusion

The patent applies a composite protective film structure consisting of multiple layers with different materials and orientations. Specifically, it uses a first protective film (amorphous Al2O3), a second protective film (crystalline AlN with c-axis orientation), and a third protective film (amorphous Al2O3). This composite structure combines the oxygen barrier properties of amorphous Al2O3 with the light absorption resistance of crystalline AlN, achieving both ease of manufacture and high reliability by preventing both oxygen diffusion and light absorption-induced damage.

The patent applies different material properties to different layers of the protective film to address specific local requirements. The amorphous Al2O3 layers provide oxygen barrier functions, while the crystalline AlN layer provides light absorption resistance. Each layer is optimized for its specific function, creating a multi-functional protective system that addresses both oxygen diffusion and light absorption issues at the resonator end face.

The patent employs a three-layer composite protective film structure where each layer serves a specific function. The first amorphous Al2O3 layer blocks oxygen diffusion, the middle crystalline AlN layer prevents light absorption and thermal reduction, and the third amorphous Al2O3 layer provides additional oxygen barrier protection. This composite structure achieves comprehensive protection against both oxygen diffusion and light absorption without requiring overly complex additional components.

The protective film is segmented into three distinct layers, each with specific material composition and orientation characteristics. This segmentation allows each layer to specialize in preventing specific deterioration mechanisms, with the amorphous layers handling oxygen barrier functions and the crystalline layer handling light absorption resistance, thereby achieving reliable multi-functionality through structured division.

The patent creates a composite protective film system where the crystalline AlN layer with c-axis orientation provides the oxygen barrier property, while the amorphous Al2O3 layers surrounding it provide light absorption resistance. This composite arrangement allows the crystalline AlN to maintain its oxygen barrier function while being protected from light absorption-induced thermal reduction by the amorphous Al2O3 layers, thereby preventing catastrophic optical damage.

The amorphous Al2O3 layers act as intermediary protective layers between the external environment and the crystalline AlN layer. These intermediary layers absorb and dissipate light energy before it reaches the crystalline AlN, preventing thermal reduction of the band gap and subsequent light absorption acceleration that would lead to COD, while allowing the crystalline AlN to maintain its oxygen barrier function.