研究目的
Demonstrating a thin-film flip-chip UVB LED with substrate removal achieved by electrochemical etching of a sacrificial AlGaN layer to improve light extraction efficiency.
研究成果
The study successfully demonstrated a thin-film flip-chip UVB LED with substrate removal achieved by electrochemical etching, showing no degradation of structural and optical properties. The process is applicable to deep-UV LEDs and other devices benefiting from high-quality III-nitride device layers.
研究不足
The high series resistance of the LED was attributed to high contact resistance caused by a non-optimized annealing temperature and n-contacts on low-doped, N-polar AlGaN. An alternative process flow could solve this issue.
1：Experimental Design and Method Selection:
The study involved the design and fabrication of a thin-film flip-chip UVB LED using electrochemical etching for substrate removal. The methodology included epitaxial layer growth, device fabrication, and electrochemical etching processes.
2：Sample Selection and Data Sources:
The samples were AlGaN-based LED structures grown on AlN/sapphire substrates, with specific doping levels and compositions for the sacrificial and etch stop layers.
3：List of Experimental Equipment and Materials:
Equipment included a 3 × 200 close-coupled showerhead reactor for epitaxial growth, standard photolithography and reactive ion etching for device fabrication, and a Biologic potentiostat for electrochemical etching. Materials included trimethylaluminium, trimethylgallium, trimethylindium, ammonia, silane, and cyclopentadienylmagnesium.
4：Experimental Procedures and Operational Workflow:
The process flow included epitaxial growth, mesa definition, contact deposition, SiO2 protection layer deposition, electrochemical etching, and flip-chip bonding.
5：Data Analysis Methods:
Electroluminescence spectra and photoluminescence decay times were measured to assess the optical and structural properties of the LEDs.
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