《厦门大学学报（自然科学版）》

发光效率是LED器件的核心指标,为了提升GaN-LED的发光效率,研究了具有不同V型缺陷密度的材料与器件的光致发光及电致发光特性,分析了影响发光效率的因素,研究发现V型缺陷一方面通过提升载流子(特别是空穴)注入效率而改善发光效率,另一方面又会通过减少有效发光面积而降低发光效率,这一竞争机制共同影响具有V型缺陷结构的GaN-LED的发光效率.结果表明,尺寸为0.25 mm×0.75 mm的芯片在150 mA驱动条件下,随着V型缺陷密度的增加,发光功率和外量子效率先上升后下降.对于最优化缺陷密度(4.2×108 cm-2)的样品,其发光功率和外量子效率分别为183.5 mW和45.0%,较最小缺陷密度(1.7×108 cm-2)样品的发光功率172.2 mW和外量子效率42.2%,均约提升6.6%.

Luminescence efficiency is one of the key indicators of LEDs.For improving the luminescence efficiency of GaN-LEDs,photoluminescence and electroluminescencecharacteristics of materials and devices with various V-defect densities are studied.One competitive mechanism is revealed.In one hand,the injection efficiency promotion of carriers(hole mainly)due to the increased V-defectdensity results in the increase of luminescence efficiency.On the other hand,the area decrease of the active region due to the increased V-defectdensity leads to the decrease of luminescence efficiency.LED chips are fabricated with identical size of 0.25 mm×0.75 mm,and are drived at the current of 150 mA.With the increase of the V-defect density,the light output and the external quantum efficiency are improved first and then decreased.The best light output and external quantum efficiency of chips with the V-defect density of 4.2×108 cm-2are shown as 183.5 mW and 45.0% respectively,which are 6.6% better than those of 172.2 mW and 42.2% of chips with un-optimized V-defect density of 1.7×108 cm-2.

引言
1 实验
2 结果与分析
3 结论

图1 GaN-LED外延片样品的结构示意图<br/>Fig.1 Schematic diagram of GaN-LED Epi-structures

图1 GaN-LED外延片样品的结构示意图
Fig.1 Schematic diagram of GaN-LED Epi-structures

图2 SEM表征的样品SS1～SS4的V型缺陷密度<br/>Fig.2 V-pits densities of SS1～SS4 characterized by SEM

图2 SEM表征的样品SS1～SS4的V型缺陷密度
Fig.2 V-pits densities of SS1～SS4 characterized by SEM

图3 样品SS1～SS4在不同激发功率密度条件下PL的λp(a)、PL强度和相对IQE的变化(b)<br/>Fig.3 Laser power density dependence of PL peak wavelength PL intensity and relative IQF for samples SS1～SS4

图3 样品SS1～SS4在不同激发功率密度条件下PL的λp(a)、PL强度和相对IQE的变化(b)
Fig.3 Laser power density dependence of PL peak wavelength PL intensity and relative IQF for samples SS1～SS4

图4 S1～S4芯片样品在150 mA特征电流驱动条件下的光电性能与V型缺陷密度的对应关系<br/>Fig.4 Dependence relationships between the electronic-optical parameters of S1～S4 chips drived at 150 mA with varied V-pits densities

图4 S1～S4芯片样品在150 mA特征电流驱动条件下的光电性能与V型缺陷密度的对应关系
Fig.4 Dependence relationships between the electronic-optical parameters of S1～S4 chips drived at 150 mA with varied V-pits densities