垂直结构GaN基LED用Ni / Ag反射镜电极

Abstract

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) Omega·cm~2,同时在450 nm处反射率为93%。

The Ni/ Ag/ Ti/ Au metal reflector electrode is widely used in the; GaN-based vertical structured light-emitting diode(LED), traditional; fabrication process. However, the formation of ohmic contact with high; quality needs a high temperature and long time annealing, which; deteriorates the reflectivity of the reflector and the performance of; the device. A new method based on the concept of decoupling the; reflector electrode into a contact layer and a reflection layer was; introduced, and the annealing time and the temperature were reduced by; this method. The reflector electrode with good ohmic contact; characteristics and high reflectivity was obtained, which solved the; problem that the optical and electrical properties of the conventional; electrode were mutually restricted. Firstly, an extremely thin Ni/ Ag; contact layer was deposited as the contact layer. After long-time; annealing with high temperature for the contact layer, the thick layer; Ag metal was deposited as the reflecting layer, then followed by a low; temperature annealing. In the above process, the refecting layer, which; plays a major role in the reflection, is free from high temperature and; long time annealing. Compared with the traditional Ni/ Ag/ Ti/ Au; electrode, the method achieves better ohmic contact and greatly improves; the reflectivity of the electrode. After annealing of the contact layer; at 500 ℃ for 3 min and annealing of the whole structure at 400 ℃ for 1; min, both in oxygen atmosphere, the specific contact resistivity of the; electrode reaches 1.70*10~(-3) Omega·cm~2 and the reflectivity reaches; 93% at the wavelength of 450 nm.