Quantum Dot Lasers Epitaxially Grown on Silicon
Author(s) Liu, Alan Young Advisor(s) Bowers, John Abstract: This thesis investigates the growth, fabrication, and performance of III V semiconductorquantum dot lasers epitaxially grown on silicon based substrates as an enablingtechnology for the realization of low cost, size, weight, and power (cSWaP) photonic integrated circuits. The use of large area, low cost silicon or silicon on insulator (SOI) basedsubstrates as a photonic integration platform is attractive due to existing economies ofscale and potential to recycle advanced CMOS fabrication tools already developed forsilicon microelectronics. The indirect bandgap of silicon presents a major hurdle towardsthe complete integration of photonic devices on silicon in particular a laser. To circumvent inefficient light emission from silicon's indirect bandgap, current methods tofabricate silicon based lasers typically rely on a separate material for the generation andamplification of light. These methods include integration of III V materials onto siliconvia wafer bonding or direct epitaxial growth, as well as band gap engineering of groupIV elements such as Ge or GexSn(1 x) grown on silicon for direct gap light emission.Direct growth of high gain III V compound semiconductors onto silicon substratesis well suited for high volume applications. Unfortunately, large dislocation densitiestypically result from the growth process due to fundamental material differences betweenIII Vs and Si, which is detrimental to both the device efficiency as well as reliability.In this thesis, we demonstrate III V laser diodes epitaxially grown on silicon with worldrecord performance. Key to our approach is the use of III V self assembled quantumdot light emitters in place of traditional quantum wells, offering advantages of reduced sensitivity to dislocations, reduced sensitivity to reflections/optical feedback, and lowvalues of threshold current (densities) In particular, the reduced sensitivity of quantumdot active regions to dislocations allows us to employ direct epitaxial growth for theintegration of III V quantum dot lasers on silicon substrates with minimal compromisein light emission efficiency.