Study of Si-Based GeSn Optically Pumped Lasers With Micro-Disk and Ridge Waveguide Structures

Abstract

A silicon-based monolithic laser has long been desired. Recent demonstration of lasing from direct bandgap group-IV alloy GeSn has opened up a completely new approach that is different from the traditional III-V integration on Si. In this study, high-quality GeSn samples were grown using a unique spontaneous Sn-enhanced growth recipe with an Sn composition as high as ∼20.0%. GeSn lasers based on waveguide Fabry-Pérot and micro-disk cavities were fabricated and characterized. The waveguide features better local heat dissipation, while the micro-disk offers stronger optical confinement plus strain relaxation. The maximum operating temperature of 260 K was achieved from a waveguide laser, and a threshold of 108 kW/cm 2 at 15 K was achieved from a micro-disk laser. A peak lasing wavelength of up to 3.5 µm was obtained with a 100-µm-wide ridge waveguide laser.

Reduced Lasing Thresholds in GeSn Microdisk Cavities with Defect Management of the Optically Active Region

“…In this work, the thicknesses are very similar to those reported in ref. 5 The optical pumping conditions are also similar, only the duty cycle is much higher here. Note that it is not favorable, since as discussed in the SI, a higher duty cycle induces heating of the gain media as compared the low duty cycle used in previous reports.…”

“…More data and details on experimental conditions used for previous works can be found in the comparison table reported in ref. 5 Black, grey and light blue squares are current values. The dashed line is drawn to show the trend.…”

“…The latter yielded a very high selective etching of Ge over GeSn, 23 and was thus selected as the best option to fabricate suspended GeSn microdisks in the literature. 5 However, such an etching chemistry does not enable to etch the bottom defective interface in GeSn as discussed in ref. 22 On the other hand, the SF 6 gas is less selective and enables, as discussed in the following, to remove the defective interface from the active region of the GeSn microdisks.…”

“…This energy splitting increases with the Sn content in strain-free GeSn alloys. 3,4 This very attractive feature has been the subject of numerous researches, the aim being to fabricate lasers compatible with group IV elements and complementary metal oxide semiconductor (CMOS) process [5][6][7] which has recently led to an electrically injected source. 8 As the Sn solubility in Ge is limited to only 1 %, i.e.…”

Review of Si-Based GeSn CVD Growth and Optoelectronic Applications

“…Encouraged by this major technical breakthrough, researchers used the injection methods such as optical injection with a Ge laser to check the GeSn waveguide, and lasing behavior was clearly observed at a low temperature in 2015 [ 70 ]. Following this breakthrough, several types of GeSn lasers [ 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ] were demonstrated, though they still suffer from the problems of low-temperature operation and high lasing thresholds. To overcome these difficulties, several methods have been proposed to improve performance, such as greater Sn incorporation into Ge [ 73 , 75 , 76 ], the use of SiGeSn/GeSn/SiGeSn heterostructures or SiGeSn/GeSn/SiGeSn MQWs as the gain medium [ 83 , 84 , 85 , 86 ], a modulation doping scheme in SiGeSn/GeSn/SiGeSn MQWs [ 87 ], defect management [ 80 ], and thermal management [ 81 , 82 ].…”