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利用低压MOCVD系统在弯曲度值不同的蓝宝石衬底上生长了GaN基LED外延结构并制作芯片。测量了芯片的主要电学和光学参数,并分析了衬底弯曲度值对芯片性能的影响。分析结果表明:存在弯曲度的衬底预先弛豫了外延层中的部分应力,改善了外延层的质量,从而提高了LED芯片的性能。随着衬底弯曲度值的逐渐增加,下层GaN对有源层中InGaN材料的压应力作用不断减小,导致芯片的主波长逐渐发生蓝移。
The low-pressure MOCVD system was used to grow GaN-based LED epitaxial structures and fabricate chips on sapphire substrates with different curvatures. The main electrical and optical parameters of the chip were measured, and the influence of substrate curvature on the chip performance was analyzed. The analysis results show that the substrate with bending degree pre-relax some of the stress in the epitaxial layer and improve the quality of the epitaxial layer, thereby improving the performance of the LED chip. With the gradual increase of substrate curvature, the compressive stress of the underlying GaN on the InGaN material in the active layer decreases, resulting in the gradual blue shift of the dominant wavelength of the chip.