School of Electrical Engineering, Korea University , Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea.
ACS Appl Mater Interfaces. 2014 Oct 8;6(19):16601-9. doi: 10.1021/am5031165. Epub 2014 Sep 25.
This paper reports improvements in the electrical and optical properties of blue-emission gallium nitride (GaN)-based thin-film light-emitting diodes (TFLEDs) after laser-based Si doping (LBSD) of a nitrogen-face n-GaN (denoted as hereafter n-GaN) layer. Experimental results show that the light-output powers of the flat- and rough-surface TFLEDs after LBSD are 52.1 and 11.35% higher than those before LBSD, respectively, at a current of 350 mA, while the corresponding operating voltages are decreased by 0.22 and 0.28 V for the flat- and rough-surface TFLEDs after LBSD, respectively. The reduced operating voltage after LBSD of the top n-GaN layer may result from the remarkably decreased specific contact resistance at the metal/n-GaN interface and the low series resistance of the TFLED device. The LBSD of n-GaN increases the number of nitrogen vacancies, and Si substitutes for Ga (SiGa) at the metal/n-GaN interface to produce highly Si-doped regions in n-GaN, leading to a decrease in the Schottky barrier height and width. As a result, the specific contact resistances are significantly decreased to 1.56 × 10(-5) and 2.86 × 10(-5) Ω cm(2) for the flat- and rough-surface samples after LBSD, respectively. On the other hand, the increased light-output power after LBSD can be explained by the uniform current spreading, efficient current injection, and enhanced light scattering resulting from the low contact resistivity, low lateral current resistance, and additional textured surface, respectively. Furthermore, LBSD did not degrade the electrical properties of the TFLEDs owing to low reverse leakage currents. The results indicate that our approach could potentially enable high-efficiency and high-power capabilities for optoelectronic devices.
本文报道了在氮面 n-GaN（以下简称 n-GaN）层进行激光基 Si 掺杂（LBSD）后，蓝色发射 GaN 基薄膜发光二极管（TFLED）的电学和光学性能的改善。实验结果表明，在电流为 350 mA 时，经过 LBSD 后，平整表面和粗糙表面 TFLED 的光输出功率分别比 LBSD 前提高了 52.1%和 11.35%，而相应的工作电压分别降低了 0.22 V 和 0.28 V。经过 LBSD 处理后，顶部 n-GaN 层的工作电压降低，可能是由于金属/n-GaN 界面的特定接触电阻显著降低和 TFLED 器件的串联电阻降低。n-GaN 的 LBSD 增加了氮空位的数量，Si 在金属/n-GaN 界面处取代 Ga（SiGa），在 n-GaN 中产生高 Si 掺杂区域，导致肖特基势垒高度和宽度减小。结果，平整表面和粗糙表面样品经过 LBSD 后，特定接触电阻分别显著降低至 1.56×10(-5)和 2.86×10(-5)Ωcm(2)。另一方面，经过 LBSD 后光输出功率增加，可以解释为低接触电阻率、低横向电流电阻和附加纹理表面分别导致均匀的电流扩展、有效的电流注入和增强的光散射。此外，由于反向漏电流低，LBSD 没有降低 TFLED 的电性能。结果表明，我们的方法有可能为光电设备实现高效率和高功率性能。
