Silisyum germanyum çoklu kuantum kuyuları içeren yüksek verimli optoelektronik aygıtlar

Silicon (Si) based complementary metal-oxide-semiconductor (CMOS) technology provides a low cost platform and reproducible processing for electronic signal processing and electronic industry has significantly flourished in terms of increased device densities and speeds. All the same, advanced CMOS processes associated with the very large scale integrated (VLSI) circuits are required for the fabrication of today?s advanced microprocessors comprising billions of transistors per single chip with higher operational data rates. Herein, increasing trend for the speed of current circuits is hampered due to the delays of electrical interconnects that basically arise from RC factor. Signal attenuation due to power dissipation and electromagnetic interference issues are further physical bottlenecks that affect the performance of current technology. At this point, an idea proposes the development of optical interconnect network layers on Si CMOS circuitry operating at telecommunications wavelength range (~1.3-1.5 ?m). This promising conception enables optical information processing and offers a platform that overcomes the physical restrictions of electrical interconnects. Si based optoelectronic devices are near-infrared-blind due to large indirect (~1.12 eV) and direct band gap (~3.4 eV) energies. To date, III-V compounds and especially InGaAs based detectors are ?state-of-the-art? optical devices that are used for near-infrared (NIR) applications. However, due to high material cost and difficult integration with Si CMOS technology they have limited market growth. At this point, germanium (Ge) is a promising candidate for NIR applications with its suitable indirect (~0.66 eV) and direct (~0.8 eV) band gap, which overcomes spectral limitations of Si. Additionally, lattice mismatch (~4.2%) problem among Si and Ge is worked out by novel heteroepitaxial growth technique (MHAH), which reduces the threading dislocations and enables the monolithic integration with conventional CMOS technology. For the scope of the thesis, fabrication, material characterization and device characterizations of p-i-n photodetector and electro-absorption modulator architectures, which are the key elements of a basic optical interconnect structure, are performed. Ge/SixGe1-x multi quantum well (MQW) structures are utilized in the intrinsic layer to exploit the electro-absorption mechanism of quantum-confined Stark effect (QCSE). Represented photodetectors exhibit low dark current (~5 mA/cm2 at -1 V) and high responsivity (~0.33 A/W at 1310 nm and 0 V). Demonstrated electro-absorption modulators exhibit very high absorption coefficient contrast (3.41 at 1550 nm and 3 V) especially for conventional C-band (1530-1565 nm) telecommunication wavelength range and low insertion loss (0.2 dB at 1540 nm). Modulation performance is highly comparable with the electro-absorption modulators based on direct gap III-V compounds at the wavelength range of interest. Demonstrated photodetector and electro-absorption modulators are the high performance building blocks of an optical interconnect system.