研究目的
Investigating the influence of residual stress on the performance of InGaN-based red LEDs by changing the thickness of the underlying n-GaN layers.
研究成果
The study demonstrates that reducing the in-plane residual compressive stress in the underlying GaN layers by increasing their thickness improves the crystalline quality and performance of InGaN-based red LEDs. The light-output power and external quantum efficiency of the LEDs were enhanced, with a peak emission wavelength of 633 nm achieved at 20 mA.
研究不足
The study is limited to InGaN-based red LEDs grown on c-plane patterned sapphire substrates. The performance improvements are attributed to reduced in-plane residual stress, but other factors such as defect density and material quality also play a role.
1：Experimental Design and Method Selection:
The study involved growing LED structures via metalorganic vapor-phase epitaxy (MOVPE) and characterizing them using x-ray diffraction (XRD), scanning transmission electron microscopy (STEM), atomic force microscopy (AFM), and electroluminescence (EL) measurements.
2：Sample Selection and Data Sources:
The samples were InGaN-based red LEDs grown on c-plane patterned sapphire substrates with varying thicknesses of underlying n-GaN layers.
3：List of Experimental Equipment and Materials:
The precursors for Ga, Al, In, and N were trimethylgallium (TMGa), trimethylaluminum (TMAl), trimethylindium (TMIn), and ammonia (NH3), respectively. The precursors for n- and p-type doping were silane and bis-cyclopentadienyl magnesium, respectively.
4：Experimental Procedures and Operational Workflow:
The LED structures were grown in a single-wafer horizontal reactor. The thickness of the underlying n-GaN layers was varied from 2 to 8 lm. The crystalline quality and performance of the LEDs were then evaluated.
5：Data Analysis Methods:
The in-plane residual stress was calculated using XRD measurements. The EL intensity, peak wavelength, and full width at half maximum (FWHM) were characterized to evaluate the LED performance.
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