湿法氧化Al0.85Ga0.15As时SiO2层的保护作用

本文研究了有无氧化硅保护层时Al0.85Ga0.15As层的高温湿法氧化。实验结果表明：氧化硅层对Al0.85Ga0.15As层的高温侧向湿法氧化速率基本无影响;被氧化区域SEM图像的衬度和有氧化硅保护层样品As拉曼峰的缺乏归因于被氧化区域中不存在氧化反应产物As,这有利于提高氧化层的热稳定性;有SiO2保护层样品的发光强度比无SiO2保护层样品的发光强度强的多,且具有SiO2保护层样品的发光峰位和半高全宽与氧化前的样品基本一致,而无SiO2保护层样品的发光峰位红移,半高宽展宽,这是由于氧化硅层阻止了GaAs盖层的氧化。     

有效折射率微扰法研究单缺陷光子晶体平板微腔的性质

应用有效折射率微扰法结合二维/三维平面波方法研究了施主和受主缺陷型H1微腔的性质, 使用修正后的有效折射率可以准确地计算微腔的腔模频率, 与三维全矢量时域有限差分法的计算结果很相近. 对于施主型H1微腔, 以介质带边为匹配标准修正的有效折射率计算的微腔腔模频率误差最小, 而对于受主型H1微腔, 匹配标准则应设置为中间带. 有效折射率微扰法既可以将计算的维度从三维降到二维, 大大减少计算所需的计算机内存和时间, 又可以保持计算结果的准确性, 这对于光子晶体微腔的广泛应用具有非常重要的价值.     

Protection effect of a SiO_2 layer in Al_(0.85)Ga_(0.15)As wet oxidation

正The Al_(0.85)Ga_(0.15)As layers buried below the GaAs core layer with and without the SiO_2 layer were successfully oxidized in a wet ambient environment.The experimental results show that the SiO_2 layer has little impact on the lateral-wet-oxidation rate of the Al_(0.85)Ga_(0.15)As layer.The contrast of the SEM image of the oxidized regions and the absence of As-related Raman peaks for samples with the SiO_2 layer arise from the removal of As ingredients with the largest atomic number,which leads to improvements in the thermal stability of the oxidized layer.The PL intensities of samples with the SiO_2 layer are much stronger than those without the SiO_2 layer.The PL emission peak is almost unshifted with a slight broadening under the protection of the SiO_2 layer.This is attributed to the SiO_2 layer preventing oxidation damage to the GaAs capping layer.     

Anomalous temperature dependence of photoluminescence spectra from InAs/GaAs quantum dots grown by formation–dissolution–regrowth method

Two kinds of InAs/GaAs quantum dot(QD) structures are grown by molecular beam epitaxy in formation–dissolution–regrowth method with different in-situ annealing and regrowth processes. The densities and sizes of quantum dots are different for the two samples. The variation tendencies of PL peak energy, integrated intensity, and full width at half maximum versus temperature for the two samples are analyzed, respectively. We find the anomalous temperature dependence of the InAs/GaAs quantum dots and compare it with other previous reports. We propose a new energy band model to explain the phenomenon. We obtain the activation energy of the carrier through the linear fitting of the Arrhenius curve in a high temperature range. It is found that the Ga As barrier layer is the major quenching channel if there is no defect in the material. Otherwise, the defects become the major quenching channel when some defects exist around the QDs.