GaN/In_xGa_(1-x)N型最后一个量子势垒对发光二极管内量子效率的影响

GaN/In_xGa_(1-x)N型最后一个量子势垒结构能有效提高发光二极管(LED)器件内量子效率,缓解LED效率随输入电流增大而衰减的问题.本文综述了该结构及其结构变化——In组分梯度递增以及渐变、GaN/In_xGa_(1-x)N界面极化率改变等对改善LED器件性能的影响及优势,归纳总结了不同结构的GaN/In_xGa_(1-x)N型最后一个量子垒的工作机理,阐明极化反转是该结构提高LED性能的根本原因.在综述该结构发展的基础之上,通过APSYS仿真计算,进一步探索和深入分析了该结构中In_xGa_(1-x)N层的In组分及其厚度变化对LED内量子效率的影响.结果表明:In组分的增加有助于在GaN/In_xGa_(1-x)N界面产生更多的极化负电荷,增加GaN以及电子阻挡层处导带势垒高度,减少电子泄漏,从而提高LED的内量子效率;但GaN/In_xGa_(1-x)N型最后一个量子势垒中In_xGa_(1-x)N及GaN层厚度的变化由于会同时引起势垒高度和隧穿效应的改变,因而In_xGa_(1-x)N和GaN层的厚度存在一个最佳比值以实现最大化的减小漏电子,提高内量子效率.     

弹性应变及结构参数对InAs/GaAs应变层超晶格能带结构的影响

本文报道弹性应变及结构参数对 InAs/GaAs应变层超晶格导带、价带不连续性及其子能带结构的影响.通过分析流体静应力和单轴应力对体材料带边能带位置的影响,确定了 InAs/GaAs超晶格导带及价带能量不连续性,并用包络函数法计算了该超晶格的子能带结构.结果表明:这些量不仅依赖于组成超晶格的两种材料的体性质,而且还依赖于超晶格的晶格常数,势阱、势垒宽度以及材料的应变;通过调节InAs层与 GaAs层的层厚之比,可以使 InAs/GaAs超晶格价带轻空穴处于第Ⅱ类超晶格势当中,从而实现轻空穴与电子、重空穴的空间分离.     

热氧化GaN制备的β-Ga2O3基日盲紫外探测器

利用热氧化法将电化学腐蚀制备的多孔GaN薄膜氧化成三维孔隙状β-Ga₂O₃薄膜,分析了多孔GaN薄膜与传统GaN薄膜在氧化机理上的区别,并通过材料表征证明了多孔GaN薄膜能够实现更快的氧化速率。随后将氧化生成的β-Ga₂O₃薄膜制备成MSM型β-Ga₂O₃基日盲紫外探测器,在260nm光照及10V偏压下,器件的响应度为16.9A/W,外量子效率为8×10³%,探测率D*达到了2.03×10¹⁴Jones,能够满足弱光信号的探测需求。此外,器件的瞬态响应具有非常好的稳定性,相应的上升时间为0.75s/4.56s,下降时间为0.37s/3.48s。     

分子束外延Ga_(1-x)In_xAs_(1-y)Sb_y材料的傅里叶变换红外光谱

报道了(100)半绝缘GaAs衬底和(100)掺Te GaSb衬底上分子束外延法生长的Ga_(1-x)In_xAs_(1-y)Sb_y材料的傅里叶变换红外光谱特性,分析解释了引起两种衬底上Ga_(1-x)In_xAs_(1-y)Sb_y外延材料红外光谱差异的原因.实验确定了这种材料的带隙和相应波长,与内插法计算的结果进行了比较,发现所有样品的实验值均偏大于理论值,对此进行了理论探讨.     

A polarization mismatched p-GaN/p-Al0.25Ga0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa

A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes (μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency (EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure for 445 nm GaN-based μLEDs with the size of $40 \times 40 $μm$^{2}$, which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure provides holes with more energy and can facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al$_{0.25}$Ga$_{0.75}$N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs.