Development of group-III- nitride-based nanostruchue-embedded phosphor particles

与传统的由均匀材料组成的颗粒组成的粉末荧光粉不同，GaN基纳米结构嵌入颗粒由于载流子限制效应而被认为具有更高的发光效率。作为制备这种颗粒的基本技术，用气相法制备了以下三个过程：(1)在第一反应器中，由蒸发的Al和N_2气体在1100-1250℃的温度(T_1)下反应生成了氮化铝颗粒。虽然在1100℃下制备的样品是氮化铝颗粒和未反应铝的混合物，但在T_1高于1150℃时制备的样品是单相氮化铝。从制备高质量氮化铝颗粒的角度来看，反应温度为1200℃是有利的。(2)在第二步反应中，通过氯化镓和氨气在1000℃的反应在氮化铝核心颗粒上生长GaN。可以看出，氮化铝芯层的颗粒直径从0.10.2μm增大。这样制备的GaN/AlN双层粒子显示出以GaN的带边发射为主的阴极发光，表明生长的GaN具有较高的结晶质量。(3)AlCl3和NH3在第二反应器的下游部分反应在GaN粒子表面沉积了AlN。AlN包覆颗粒的光致发光以GaN的带边发射为主。AlCl3供应速率对发光性质的依赖关系表明，表面势垒对激发载流子和钝化对表面缺陷的影响。

In contrast to the conventional powder phosphors consisting of particles with a uniform material composition, GaN-based nanostructure-embedded particles, which consist of GaN quantum dots or quantum wells in the AlN matrix, has been proposed to have higher luminescence efficiencies owing to the carrier confinement effect. As a fundamental technique to fabricate such particles, the following three processes have been demonstrated by using the vapor phase method.(1) The AlN particles were first formed by a reaction of vaporized Al and N_2 gas at temperatures (T_1) from 1100 to 1250℃ in the first reactor. Although the sample prepared at 1100℃ is a mixture of AlN particles and unreacted Al, those prepared at T_1 higher than 1150℃ are a single phase AlN. It was found that the reaction temperature of 1200℃ is favorable from a viewpoint of producing the high quality AlN particles.(2) At the second step, GaN was grown on the AlN core particles by a reaction of GaCl and NH_3 at 1000℃ in the second reactor. It can be seen that the particle diameter was increased from 0.1-0.2 μm for the AlN core. Thus fabricated GaN/AlN bilayer particles showed cathodoluminescence dominated by the band edge emission of GaN, indicating a high crystalline quality of the overgrown GaN.(3) AlN was deposited on the surface of GaN particles by a reaction of AlCl_3 and NH_3 in the downstream part of the second reactor. AlN-coated particle showed photoluminescence (PL) dominated by the band edge emission of GaN. The dependence of AlCl_3 supply rate on the PL property suggests the effects of surface barrier to the excited carriers and passivation to surface defects.