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Ni/Ag/Ti/Au金属系反射镜电极广泛用于GaN基垂直结构发光二极管(LED)的传统制造工艺。这种电极需要进行高温长时间整体退火才能获得高质量的欧姆接触,但对电极的反射率和器件性能影响较大。介绍了一种新工艺方法,该方法将电极分解为接触层和反射层,降低反射层经历的退火温度和时间,获得了拥有良好的欧姆接触特性和高反射率的反射镜电极,解决了传统电极光学性能和电学性能相互制约的问题。首先生长极薄的Ni/Ag作为接触层,对接触层进行高温长时间退火后再生长厚层Ag作为反射层,之后再进行一次低温退火。使得对反射起主要作用的反射层免于高温长时间退火,相较于传统Ni/Ag/Ti/Au电极,该方法在获得更优良的欧姆接触的同时,提升了电极的反射率。在氧气氛围下进行500℃接触层退火3 min,400℃整体退火1 min后,电极的比接触电阻率为1.7×10~(-3)Ω·cm~2,同时在450 nm处反射率为93%。
Ni / Ag / Ti / Au metal-based mirror electrodes are widely used in traditional manufacturing processes for GaN-based vertical structure light-emitting diodes (LEDs). Such electrodes require high temperature and long time overall annealing in order to obtain high quality ohmic contacts, but the electrode reflectance and device performance have a greater impact. A new process method is introduced, which decomposes the electrode into a contact layer and a reflection layer, and reduces the annealing temperature and time experienced by the reflection layer, thereby obtaining a mirror electrode with good ohmic contact characteristics and high reflectivity, Electrode optical and electrical properties of mutual constraints. First, an extremely thin Ni / Ag layer is grown as a contact layer, the contact layer is annealed at a high temperature for a long time, and then a thick Ag layer is grown as a reflective layer, followed by a low temperature annealing. So that the reflective layer that plays a major role in the reflection is prevented from being annealed for a long time at high temperature. Compared with the conventional Ni / Ag / Ti / Au electrode, the method improves the reflectivity of the electrode while obtaining better ohmic contact. The contact resistivity of the electrode was 1.7 × 10 ~ (-3) Ω · cm ~ 2 after annealed at 500 ℃ for 3 min in oxygen atmosphere and annealed at 400 ℃ for 1 min. The reflectance at 450 nm was 93%.