MOCVD heteroepitaxy of GaAs/InP templates for integration of lasers on (001) Si substrates

Abstract

Highly integrated silicon-based photonic integrated circuits (PICs) are desirable for large-capacity data communications due to their superiority in low latencies, low-power consumption, and unprecedentedly high bandwidth compared to conventional electronic interconnects. There is a rapidly expanding research interest in the diverse applications of Si-based PICs. These applications span within a wide range of areas such as high-speed communication, quantum technologies, and optical sensing. In recent years, the integration of III-V materials on large-diameter Si substrates has been a topic of intense study, capitalizing on the well-established CMOS manufacturing capabilities. However, due to the indirect band structure of Si, the realization of an efficient light source has been a challenge. Over the past three decades, various techniques have been developed to directly integrate III-V alloys onto (001) Si substrates, offering a potential solution to overcome this limitation. Initially, an extensive investigation was carried out on the heteroepitaxy of GaAs and InP on commercial nominal (001) planar Si substrates using MOCVD in this thesis. The effects of thermal cycle annealing at high temperatures and InGaAs/GaAs strained-layer superlattices on the defect density and morphology of GaAs/Si templates were investigated. Based on the optimized GaAs/Si templates, InP QD microdisk lasers (MDLs) were fabricated on the templates, with the lowest threshold of 0.5 μW in continuous-wave (CW) mode at room temperature (RT). Subsequently, electrically pumped 980 nm QW lasers, operating in CW mode at 95 °C, were successfully demonstrated on (001) Si using strained-compensated InGaAs/GaAs/GaAsP QW structure. Moreover, we investigated the device performance of InAs/InAlGaAs quantum dash MDLs on the InP/Si templates. Lastly, the in-plane GaAs crystal was selectively grown on patterned SOI by the lateral aspect ratio trapping technique for future fully integrated Si-based PICs. A threshold of 1100 μJ/cm² has been obtained on the GaAs MDLs fabricated on SOI substrates at RT.

Date of Award	2023
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Man Hoi WONG (Supervisor) & Kei May LAU (Supervisor)