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Báo cáo hóa học: " Improved ground-state modulation characteristics in 1.3 μm InAs/GaAs quantum dot lasers by rapid thermal annealing"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Improved ground-state modulation characteristics in 1.3 μm InAs/GaAs quantum dot lasers by rapid thermal annealing | Zhao et al. Nanoscale Research Letters 2011 6 382 http www.nanoscalereslett.eom content 6 1 382 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Improved ground-state modulation characteristics in 1.3 pm InAs GaAs quantum dot lasers by rapid thermal annealing Hanxue Zhao1 Soon Fatt YoonH Chun Yong Ngo2t and Rui WangH Abstract We investigated the ground-state GS modulation characteristics of 1.3 gm InAs GaAs quantum dot QD lasers that consist of either as-grown or annealed QDs. The choice of annealing conditions was determined from our recently reported results. With reference to the as-grown QD lasers one obtains approximately 18 improvement in the modulation bandwidth from the annealed QD lasers. In addition the modulation efficiency of the annealed QD lasers improves by approximately 45 as compared to the as-grown ones. The observed improvements are due to 1 the removal of defects which act as nonradiative recombination centers in the QD structure and 2 the reduction in the Auger-related recombination processes upon annealing. Introduction Quantum dots QDs are promising for realizing fast and stable laser sources in fiber optic applications due to their superior characteristics over conventional quantum well QW lasers such as low threshold current high internal efficiency and infinite characteristic temperature 1 2 . However the high-speed performance of QDs is generally poorer than that of QWs due to several factors slow inter-level relaxation of the carriers 3 finite density of state DOS and closely spaced hole energy levels 4 . Slow carrier relaxation rate in combination with the limited DOS will lead to early switching from ground-state GS lasing to excited-state ES lasing at high temperature or at high drive current. This is undesired since ES lasing reduces GS lasing efficiency due to gain saturation of the GS transition. This due to state filling effect in discrete quantum levels degrades the high-speed characteristics 2 5 of .