Study on Semiconductor Quantum Dot Lasers with Various Active Layers

• Main Authors: Chou, Bo-Tsun, 周柏存
• Other Authors: Lin, Sheng-Di
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/69822371839731428741

碩士 === 國立交通大學 === 電子研究所 === 99 === This thesis studies the quantum-dots laser diodes (QDLD) with various active layer structures. We first discuss the device characteristics of processed QDLD with cleaved facets and with various cavity lengths. The saturation gain of 3-layers、5-layers、5 p-doped and 7-layers is 7.5 cm-1、12.5 cm-1、13.6 cm-1 and 17cm-1, respectively. The characteristic temperature (T0) of QDLD are also analyzed in the range of 10-70 ℃, a highest T0 of 82 K is obtained with the laser having 5 p-doped QD layers. To study the relative intensity noise, we use high reflectivity (HR) coating on the rear facet of QDLD to reduce their threshold current and thereby to avoid the heating problem. With the HR coating, the lasers have smaller mirror loss, higher T0, higher quantum efficiency and higher photon density in cavity. Finally, we perform detailed RIN measurements on HR-coated QDLD lasing at their ground states. The model simulation gives the K and D factors from the obtained RIN data, which are related to the intrinsic 3-dB frequency and to the differential gain. As a result, we find that, as the number of QD layers increases, the laser has higher differential gain, higher saturation gain, and higher 3-dB frequency. By using p-typed doping around the QDs, the 3-dB frequency of lasers can be enhanced as well. The highest 3-dB frequency of 8.1 GHz is expected from the lasers with 7 QDs layers.