UC Santa Barbara

This thesis investigates the growth, fabrication, and performance of III-V semiconductor

quantum dot lasers epitaxially grown on silicon based substrates as an enabling

technology 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) based

substrates as a photonic integration platform is attractive due to existing economies of

scale and potential to recycle advanced CMOS fabrication tools already developed for

silicon microelectronics. The indirect bandgap of silicon presents a major hurdle towards

the complete integration of photonic devices on silicon - in particular a laser. To circumvent inefficient light emission from silicon's indirect bandgap, current methods to

fabricate silicon-based lasers typically rely on a separate material for the generation and

amplification of light. These methods include integration of III-V materials onto silicon

via wafer bonding or direct epitaxial growth, as well as band-gap engineering of group

IV 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 substrates

is well suited for high volume applications. Unfortunately, large dislocation densities

typically result from the growth process due to fundamental material differences between

III-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 world

record performance. Key to our approach is the use of III-V self-assembled quantum

dot light emitters in place of traditional quantum wells, offering advantages of reduced sensitivity to dislocations, reduced sensitivity to reflections/optical feedback, and low

values of threshold current (densities). In particular, the reduced sensitivity of quantum

dot active regions to dislocations allows us to employ direct epitaxial growth for the

integration of III-V quantum dot lasers on silicon substrates with minimal compromise

in light emission efficiency.