Mavi dalgaboyu aralığında elektrosoğrulma rekoru kıran InGaN/GaN kuvantum elektrosoğrulma kipleyicileri

Silicon based complementary metal-oxide-semiconductor (CMOS) technologyhas surely moved humankind forward in the information age. Over the years,Si CMOS has also evolved as the necessities of other technologies enabled byCMOS has expanded (for example, as the required speed of operation has in-creased). Consequently, CMOS microelectronics has been continuously replacedby their faster successors thus far. However, there is a physical limit to howfast conventional CMOS chips can run, constrained mainly due to the RC lim-itation of their electrical interconnects. This introduces a bottleneck in operat-ing speed and even downscaling interconnects does not solve this problem. Asa solution, optical clocking has been proposed and implemented commonly inthe near infrared (NIR) where optoelecronic devices are readily available. But,silicon photodetectors fabricated in standard CMOS process unfavorably sufferfrom diffusion tail problem in NIR, which limits the operating speed, prevent-ing direct high-speed clock injection into Si. To circumvent this problem, oneapproach is to utilize high-speed III-V photodetectors hybrid integrated on Sichips. This, however, introduces difficulties related to post-CMOS fabrication.iiiOn the other hand, unlike in NIR, optical clock injection directly to Si is possiblein the blue, where Si lacks the diffusion tail. However, there exists no chip-scaledevice particularly implemented to generate and inject optical clock signal blueto date. In this thesis, we propose blue InGaN/GaN based quantum electroab-sorption modulators for a possible chip-scale solution to the modulation of blueclock signal. Here we present the device conception, design, growth, fabrication,experimental characterization, and theoretical analysis of these quantum elec-troabsorption modulators. Growing on polar c-plane of its wurtzite crystal, weobtain InGaN/GaN quantum structures with zig-zag potential profile due to al-ternating polarization-induced electrostatic fields and show that their absorptionedge blue-shifts with applied electric field, unlike the red shift of conventionalquantum confined Stark effect. In such InGaN/GaN quantum structures, wedemonstrate the largest electroabsorption change of 6000 cm−1 (correspondingto 50 cm−1 absorption coefficient change for 1 V /µm field swing) around 424 nmever reported for blue. This implies that the reversed quantum confined Starkeffect in these InGaN/GaN quantum zigzag structures in the blue is comparableto the traditional quantum confined Stark effect in the InGaAsP/InP quantumwell structures in NIR commercially used in communications. These proof-of-concept demonstrations show that blue InGaN/GaN quantum electroabsorptionholds great promise for high-speed optical clock generation and injection directlyinto Si CMOS chips in the blue.Keywords: electroabsorption, III-nitrides, modulator, wells, optical clocking.iv