Ranasinghe Leonardo, Heyn Christian, Deneke Kristian, Zocher Michael, Korneev Roman, Hansen Wolfgang
Center for Hybrid Nanostructures (CHyN), University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
Nanomaterials (Basel). 2021 Mar 10;11(3):690. doi: 10.3390/nano11030690.
Epitaxially grown quantum dots (QDs) are established as quantum emitters for quantum information technology, but their operation under ambient conditions remains a challenge. Therefore, we study photoluminescence (PL) emission at and close to room temperature from self-assembled strain-free GaAs quantum dots (QDs) in refilled AlGaAs nanoholes on (001)GaAs substrate. Two major obstacles for room temperature operation are observed. The first is a strong radiative background from the GaAs substrate and the second a significant loss of intensity by more than four orders of magnitude between liquid helium and room temperature. We discuss results obtained on three different sample designs and two excitation wavelengths. The PL measurements are performed at room temperature and at = 200 K, which is obtained using an inexpensive thermoelectric cooler. An optimized sample with an AlGaAs barrier layer thicker than the penetration depth of the exciting green laser light (532 nm) demonstrates clear QD peaks already at room temperature. Samples with thin AlGaAs layers show room temperature emission from the QDs when a blue laser (405 nm) with a reduced optical penetration depth is used for excitation. A model and a fit to the experimental behavior identify dissociation of excitons in the barrier below = 100 K and thermal escape of excitons from QDs above = 160 K as the central processes causing PL-intensity loss.
外延生长的量子点（QDs）已被确立为用于量子信息技术的量子发射体，但其在环境条件下的运行仍然是一个挑战。因此，我们研究了在（001）GaAs衬底上填充AlGaAs纳米孔中的自组装无应变GaAs量子点在室温及接近室温时的光致发光（PL）发射。观察到室温运行存在两个主要障碍。第一个是来自GaAs衬底的强烈辐射背景，第二个是在液氦温度和室温之间强度显著损失超过四个数量级。我们讨论了在三种不同样品设计和两种激发波长下获得的结果。PL测量在室温以及使用廉价热电冷却器获得的200 K温度下进行。一个具有比激发绿光激光（532 nm）穿透深度更厚的AlGaAs势垒层的优化样品在室温下已经显示出清晰的量子点峰。当使用具有减小的光学穿透深度的蓝色激光（405 nm）进行激发时，具有薄AlGaAs层的样品在室温下显示出量子点发射。一个模型以及对实验行为的拟合确定，在低于100 K时势垒中激子的解离以及在高于160 K时激子从量子点的热逃逸是导致PL强度损失的核心过程。
