| abstract |
A GaN-based LED structure is provided so that the brightness and luminous efficiency of the GaN-based LED are enhanced effectively. The greatest difference between the GaN-based LEDs according to the invention and the prior arts lies in the addition of a masking buffer layer on top of the p-type contact layer and a p-type roughened contact layer on top of the masking buffer layer. The masking buffer layer could be formed using MOCVD to deposit Si x N y (x,y≧1), Mg w N z (w,z≧1), or Al s In t Ga 1-s-t N (0≦s,t<1, s+t≦1) heavily doped with Si and/or Mg. The masking buffer layer is actually a mask containing multiple randomly distributed clusters. Then, on top of the masking buffer layer, a p-type roughened contact layer made of p-type Al u In v Ga 1-u-v N (0≦u,v<1, u+v≦1) is developed. The p-type roughened contact layer does not grow directly on top of the masking buffer layer. Instead, the p-type roughened contact layer starts from the top surface of the underlying p-type contact layer not covered by the masking buffer layer's clusters. The p-type roughened contact layer then grows upward until it passes (but does not cover) the mask of the masking buffer layer for a specific distance. The total internal reflection that could have been resulted from the GaN-based LEDs' higher index of refraction than that of the atmosphere could be avoided. The GaN-based LEDs according to the present invention therefore have superior external quantum efficiency and luminous efficiency. |