Influence of growth conditions on the V-defects in InGaN/GaN MQWs

The influence of the growth temperature,TMIn/TEGa andⅤ/Ⅲratio on the V-defects of InGaN/GaN multi-quantum wells（MQWs） has been investigated and discussed.When the TMIn flow increases from 180 to 200 sccm,the density of V-defects increases from 2.72×10¹⁸ to 5.24×10¹⁸ cm^-2,and the V-defect width and depth increase too.The density also increases with the growth temperature.The densities are 2.05×10⁸,2.72×10¹⁸ and 4.23×10⁸ cm^-2,corresponding to a growth temperature of 748,753 and 758℃respectively.When the NH₃ flows are 5000,6600 and 8000 sccm,the densities of the V-defects of these samples are 6.34×10¹⁸,2.72×10¹⁸ and 4.13×10¹⁸ cm^-2,respectively.A properⅤ/Ⅲratio is needed to achieve step flow growth mode.We get the best quality of InGaN/GaN MQWs at a growth temperature of 753℃TMIn flow at 180 sccm,NH₃ flow at 6600 sccm,a flatter surface and less V-defects density.The depths of these V-defects are from 10 to 30 nm,and the widths are from 100 to 200 nm.In order to suppress the influence of V-defects on reverse current and electro-static discharge of LEDs,it is essential to grow thicker p-GaN to fill the V-defects.     

Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer

With an n-AlGaN(4 nm)/GaN(4 nm) superlattice(SL) inserted between an n-GaN and an InGaN/GaN multiquantum well active layer,the efficiency droop of GaN-based LEDs has been improved.When the injection current is lower than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL.However,as the injection current increases more than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL surpasses that of an LED without an n-AlGaN/GaN SL. The wall plug efficiency of an LED has the same trend as lumen efficiency.The improvement of the efficiency droop of LEDs with n-AlGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities.The reverse current of LEDs at -5 V reverse voltage decreases from 0.2568029 to 0.0070543μA,and the electro-static discharge(ESD) pass yield of an LED at human body mode(HBM)-ESD impulses of 2000 V increases from 60%to 90%.     

插入n-AlGaN/GaN超晶格改善GaN基LED的droop效应

在GaN基LED的n-GaN和InGaN/GaN发光区之间插入n-AlGaN/GaN超晶格来改善其droop效应。注入电流低于100mA时,插入n-AlGaN/GaN超晶格的LED的流明效率低于没有插入层的LED。注入电流高于100mA时,插入n-AlGaN/GaN超晶格的LED的流明效率高于没有插入层的LED。插入n-AlGaN/GaN超晶格后,GaN基LED在-5V的反向电压下,漏电由2.568029μA减少到0.070543μA。人体模式下,插入n-AlGaN/GaN超晶格的LED在2000V的静电电压下的通过率从60%提高到了90%。LED droop效应的改善是因为n-AlGaN/GaN超晶格过滤了穿透位错并改善了电流扩展能力。     

Effects of the p-AlInGaN/GaN superlattices’structure on the performance of blue LEDs

The advantages of the p-AIInGaN/GaN superlattices＇ （SLs） structure as an electron blocking layer （EBL） for InGaN blue light-emitting diodes （LEDs） were studied by experiment and APSYS simulation. Elec- troluminescence （EL） measurement results show that the LEDs with the p-AllnGaN/GaN SLs＇ structure EBL ex- hibited better optical performance compared with the conventional A1GaN EBL due to the enhancement of hole concentration and hole carrier transport efficiency, and the confinement of electrons＇ overflow between multiple quantum-wells （MQWs） and EBL.     

生长条件对InGaN/GaN多量子阱表面v型缺陷的影响

我们研究了生长温度、TMIn/TEGa和Ⅴ/Ⅲ比对 InGaN/GaN多量子阱表面v型缺陷的影响。当TMIn的流量从180sccm增加到200sccm,v型缺陷的密度也从2.7210¹⁸/cm² 增加到了5.2410¹⁸ /cm², v型缺陷的深度和宽度也随着TMIn流量的增加而增加。当生长温度从748℃增加到758℃, v型缺陷的密度分别是2.0510⁸/cm², 2.7210⁸/cm² 和 4.2310⁸/cm²,V型缺陷的密度随着生长温度的增加而增加。当NH3的流量从5000sccm增加到8000sccm, v型缺陷的密度分别为 6.3410¹⁸/cm², 2.7210¹⁸/cm², 4.1310¹⁸/cm²。我们在753℃, TMIn 流量为180sccm, NH3 流量为6600sccm时,得到了晶体质量最好的InGaN/GaN 多量子阱,表面平整,v型缺陷的密度也比较少。V型缺陷的深度从10nm到30nm,宽度从100nm到200nm,为了抑制v型缺陷对GaN基LEDs反向电流(IR)和静电放电 (ESD) 的影响,我们需要生长更厚的p-GaN来填充这些v型缺陷。     

Evaluation of light extraction efficiency for the light-emitting diodes based on the transfer matrix formalism and ray-tracing method

The internal quantum efficiency (IQE) of the light-emitting diodes can be calculated by the ratio of the external quantum efficiency (EQE) and the light extraction efficiency (LEE). The EQE can be measured experimentally, but the LEE is difficult to calculate due to the complicated LED structures. In this work, a model was established to calculate the LEE by combining the transfer matrix formalism and an in-plane ray tracing method. With the calculated LEE, the IQE was determined and made a good agreement with that obtained by the ABC model and temperature-dependent photoluminescence method. The proposed method makes the determination of the IQE more practical and conventional.     

AlGaN/GaN high electron mobility transistors with selective area grown p-GaN gates

We report a selective area growth (SAG) method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors (HEMTs) by metal-organic chemical vapor deposition. Compared with Schottky gate HEMTs, the SAG p-GaN gate HEMTs show more positive threshold voltage (V_th) and better gate control ability. The influence of Cp₂Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied. With the increasing Cp₂Mg from 0.16 μmol/min to 0.20 μmol/min, the V_th raises from -67 V to -37 V. The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm. The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.     

AlGaInP红、橙、黄光高亮度LED外延材料

采用金属有机化合物汽相淀积技术生长用于高亮度发光管 (UB-L ED)的 Al Ga In P/Ga As半导体微结构材料 ,突破了材料结构设计和材料生长工艺的关键技术 ,生长出满足于 Cd级的红、橙、黄光 L ED器件的外延材料。