Manipulating precursors of group-III nitrides for high-Al-content p-AlGaN toward efficient deep ultraviolet light emitters

The high-Al-content p-AlGaN electron blocking layer (EBL) is essential for mitigating electron overflow in deep ultraviolet light-emitting diodes (DUV LEDs) but suffers from poor conductivity. One of the reasons is that the carbon impurity may act as donor-like compensating defect, which is incorporated into the epilayers by the metalorganic chemical vapor deposition. To grow the high-Al-content p-EBL and minimize carbon incorporation, we proposed a group-III nitrides precursor modulation strategy. This technique involves reducing the flow rates of metalorganic precursors, trimethylaluminum, and trimethylindium, while maintaining the Al/Ga ratio. By this method, the p-Al0.8Ga0.2N EBL with an ultralow carbon concentration of 1016 cm−3 was grown. Moreover, the high initial composition in the EBL leads to a larger compositional gradient in the adjacent p-AlGaN graded layer, which increases bulk polarization-induced hole concentration compared with the p-Al0.7Ga03N EBL. Together, these factors above contribute to a 20% enhancement in light output power and a 6% reduction in operation voltage at 40 mA in the proposed DUV LED statistically. This feasible growth scheme provides a promising strategy for the high-efficiency and cost-competitive DUV LEDs.