Researches For Novel Nitride And New Structures Of High Power LED

The structure and properties of a novel ternary GeCN system have been researched and developed in this paper. The thin films of GeCN on different substrates are prepared by reactive magnetron sputtering on a sintered GeC target in N2. SEM and XPS are employed for structural characterization of the films. The SEM observations show a smooth surface morphology on the top and uniform veins on the side of GeCN films, which means a good crystal quality and a different crystalline direction with the substrates. The XPS analysis reveal the formation of complex networks among the three elements (Ge, C, N) and the existence of different chemical bonds in the GeCN films such as Ge-C,Ge-N and C=N. The XPS depth profile demonstrates a uniform stoichiometry in the films and the ratio of atom concentration is about 5:1:1 and 3:3:1. There may exist a stable phase in the films because atoms in different samples share a similar chemical environment. Then the crystal and electronic structures are calculated by Vienna ab initio Simulations Package (VASP), employing a hypothetical structure likeβ-Si3N4. The calculation results show that the lattice constant of the GeCN system decreases monotonously as the C3N4 mole fraction increases. The composition-dependent band gap exhibits a concave feature and also alternation between direct and indirect band gaps. The experiment and theoretical study suggest that the GeCN system may be a wide band gap material with a stable phase in it.In addition, we design and fabricate two new structures for high power GaN based LED chips. The novel p-n electrode and n type slot which appear like venations in a leaf blade are chose separately from four different electrode shapes and three slot scales. The novel electrodes can shorten the current route between the p type and n type electrodes and make the current spreading uniformly through the ITO or Ni/Au transparent layer to p-GaN. The n type slot can interrupt the light path of the total-reflection in the chip and make the light emit from the side wall of the slot. Both of them can improve the luminescence efficiency significantly. The optical and electrical parameters before and after encapsulation are measured and compared with works reported by other teams in the world. Total luminous flux of the 1 mm×1 mm chip is between 7~9 lumen, and the radiant flux reaches 110 milliwatt. Total luminous flux of the 0.6 mm×0.6 mm chip approach 2 lumen and the radiant flux is between 20~30 milliwatt. The parameters above achieve a high level for high power LEDs,...