Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
ACS Appl Mater Interfaces. 2013 Jun 26;5(12):5797-803. doi: 10.1021/am401354z. Epub 2013 Jun 6.
The electrical characteristics of metallization contacts to flat (F-sample, without wet-etching roughed) and wet-etching roughed (R-sample) N-polar (Nitrogen-polar) n-GaN have been investigated. R-sample shows higher contact resistance (Rc) to Al/Ti/Au (2.5 × 10(-5) Ω·cm(2)) and higher Schottky barriers height (SBH, ~0.386 eV) to Ni/Au, compared with that of F-sample (1.3 × 10(-6) Ω·cm(2), ~0.154 eV). Reasons accounting for this discrepancy has been detail investigated and discussed: for R-sample, wet-etching process caused surface state and spontaneous polarization variation will degraded its electrical characteristics. Metal on R-sample shows smoother morphology, however, the effect of metal deposition state on electrical characteristics is negligible. Metallization contact area for both samples has also been further considered. Electrical characteristics of metallization contact to both samples show degradation upon annealing. The VLED chip (1 mm × 1 mm), which was fabricated on the basis of a hybrid scheme, coupling the advantage of F- and R-sample, shows the lowest forward voltage (2.75 V@350 mA) and the highest light output power.
已研究了金属化接触到平面（F 样，未经湿法蚀刻粗糙化）和湿法蚀刻粗糙化（R 样）N 极性（氮极性）n-GaN 的电学特性。与 F 样相比，R 样的 Al/Ti/Au 接触电阻（Rc）较高（约 2.5×10^-5Ω·cm^2），Ni/Au 的肖特基势垒高度（SBH，约 0.386 eV）较高。详细研究并讨论了造成这种差异的原因：对于 R 样，湿法蚀刻工艺会导致表面态和自发极化的变化，从而降低其电学特性。R 样上的金属显示出更平滑的形态，但金属沉积状态对电学特性的影响可以忽略不计。还进一步考虑了两个样品的金属化接触面积。两种样品的金属化接触的电学特性在退火后都会退化。基于混合方案制造的 VLED 芯片（1mm×1mm）结合了 F 样和 R 样的优势，表现出最低的正向电压（2.75V@350mA）和最高的光输出功率。
