毛明華Mao, Ming-Hua臺灣大學:電子工程學研究所林彥志Lin, Yen-ChihYen-ChihLin2010-07-142018-07-102010-07-142018-07-102008U0001-1707200815085300http://ntur.lib.ntu.edu.tw//handle/246246/189059　　在本論文中，我們研究載子分佈對量子點雷射溫度特性之影響。溫度從78 K至340 K變溫量測光強度對電流的曲線圖，顯示了量子點雷射的臨界電流對溫度的關係呈現了S型曲線。我們也量測了在雙能態放光下，基態和激發態的臨界電流對溫度的關係，發現他們之間有互補的現象。這是因為載子在量子點系統內的分佈隨溫度上升會從非熱耦合過渡到熱耦合的結果。　在分光動態特性方面，低溫和室溫量測得到不一樣的結果。在低溫時，量子點系統內的載子處於非熱耦合狀態，導致各個放光群獨立放光和有相同的鬆弛振盪行為。然而在室溫下載子已達到熱耦合狀態，顯現了互補的鬆弛振盪特性。　另外我們製作了在脊狀波導上開一道平行波導的窗的雷射結構，用來研究在電流注入下量子點雷射同時受光激發影響下的動態特性。在不同溫度下的量測結果發現，室溫時量子點雷射有暫時中止激發放光的行為，而低溫時則無此現象。這是由於低溫時載子受能障侷限，不至於受光激發的熱效應而發生逃脫量子點填入更高能階的現象。　由以上的變溫量測發現，載子在量子點系統內的分佈隨溫度上升會從非熱耦合過渡到熱耦合狀態，將深遠地影響量子點雷射靜態與動態的特性。In this thesis, we investigate the influence of carrier distribution on temperature-dependent characteristics in quantum-dot lasers. From the measurement of laser light output versus injected current at temperatures of 78 K to 340 K, it shows that the behavior of threshold current of a quantum-dot laser has the S-shaped temperature dependence. We also find that the threshold currents of the ground states and the excited states versus temperature at two-state lasing condition have the complementary characteristics. This process corresponds to the transition from nonthermal to thermal coupling of carrier distribution in a quantum-dot system with increasing temperature. In the measurement of spectrally-resolved dynamic properties, we get different results at cryogenic and room temperatures. At cryogenic temperature, carriers in a quantum-dot system are in a nonthermal coupling state, and thus lasing groups lase independently and have the same relaxation oscillation behaviors. However, the carriers have reached thermal coupling at room temperature, leading to the complementary relaxation oscillation characteristics. In addition, we fabricated a windowed-stripe laser structure to study the dynamic behaviors of a quantum-dot laser under current injection and femtosecond optical pulse excitation simultaneously. We carried out measurements at different temperatures and found that quantum-dot lasers stopped lasing temporarily at room temperature while they did not have such a phenomenon at cryogenic temperature. This is because carriers are confined by the potential energy and do not have enough energy to redistribute among the quantum dots ensemble at cryogenic temperature. From the temperature-varying experiments above, we find that the transition from nonthermal to thermal coupling of carrier distribution in a quantum-dot system with increasing temperature will affect both the static and dynamic properties of a quantum-dot laser profoundly.誌謝 I要 IIIbstract IVontents VIigure Captions VIIIist of Tables XIhapter 1 Introduction 1.1 Overview 1.2 Development of Quantum-Dot Lasers 4.3 Motivation 6.4 Organization of the Thesis 7hapter 2 Theoretical Analysis of Quantum-Dot Lasers 9.1 Interaction of Carriers and Photons 9.2 Simultaneous Two-State Lasing 12.3 Homogeneous and Inhomogeneous Broadening of Optical Gain 16.4 Thermal and Nonthermal Carrier Distribution in Quantum-Dot Lasers 18hapter 3 Fabrication and Measurement of Quantum-Dot Lasers 20.1 Epitaxial Structures of Quantum-Dot Samples 20.2 Fabrication Procedures 22.3 Measuring Systems 29.3.1 Static Properties Measuring System 29.3.2 Dynamic Properties Measuring System 30hapter 4 Temperature-Dependent Characteristics in Quantum-Dot Lasers 32.1 Static Properties 32.1.1 Basic Temperature-Dependent Measurements 32.1.2 Spectrally-Resolved Static Analysis 38.1.3 Quenching of the Ground State Lasing 40.2 Dynamic Properties 45.3 Optical Excitation 49hapter 5 Conclusions 54.1 Summary of the Research 54.2 Future Work 55ibliography 57775575 bytesapplication/pdfen-US量子點雷射特徵溫度熱耦合quantum-dot lasercharacteristic temperaturethermal couplingthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/189059/1/ntu-97-R95943059-1.pdf