High-Performance Quantum Dot Lasers and Integrated Guided-Wave Devices on Silicon.

Optical interconnects, the chip-scale integration of optoelectronic devices with complementary-metal-oxide-semiconductor (CMOS) silicon circuits, provide a promising approach for the realization of the next-generation high-speed computing and communication systems. Unfortunately, optoelectronics lacks an obvious platform for monolithic integration. One of the practical solutions is the hybrid integration, through heteroepitaxial growth, of compound semiconductor optoelectronic components with silicon technology. This thesis is devoted to developing high-performance GaAs-based quantum dot lasers directly grown on silicon substrates and their monolithic integration with waveguides and electroabsorption modulators. The investigation of 1.5 μm siliconbased high-Q random photonic crystal microcavity light emitters utilizing PbSe colloidal quantum dots has also been conducted. High-performance quantum dot lasers directly-grown on silicon substrates have been achieved in this study. The performance of III-V-based lasers on silicon can be degraded by the inherent high-density propagating dislocations. To enhance device performance, a novel quantum dot dislocation filter has been developed. The best lasers exhibit relatively low threshold current density (Jth = 900 A/cm2), large small-signal modulation bandwidth of 5.5 GHz, and a high characteristic temperature (T0 = 278 K). The monolithic integration of InGaAs QD lasers with waveguides and quantum well(QW) electroabsorption modulators has been achieved through molecular beam epitaxy (MBE) growth and regrowth. Focused-ion-beam milling is utilized to create high-quality etched GaAs facets with a reflectivity of 0.28 and coupling groove with coupling coefficient greater than 20%. Quantum-dot lasers with focused-ion-beam-etched facets exhibit comparable performance to those with cleaved facets. The integrated modulator exhibits a modulation depth ~100% at 5 V reverse bias. In addition, the monolithic integration of the amorphous silicon waveguide with quantum dot laser has also been demonstrated by using plasma-enhanced-chemical-vapor deposition (PECVD). Finally, enhanced photoluminescence at 1.5 μm wavelength has been observed from PbSe colloidal quantum dots embedded in a silicon-based random photonic crystal microcavity. Such microscale light sources on silicon can also be fabricated or integrated on silicon CMOS chips, which may provide a viable route for inter- and intrachip optical communications.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60821/1/junyang_1.pd