Recently, high performance silicon based InAs /GaAs quantum dot (QD) lasers have been demonstrated with CW operation at high temperature (>75oC) and long lifetimes (>100 000 hours) by UCL and Cardiff. Here we will further develop our world leading III-V-on-Si technologies to create high performance lasers and semiconductor optical amplifiers (SOAs) for data communications applications.
Lead
Prof. Huiyun Liu (huiyun.liu@ucl.ac.uk)
Overview
The principal objectives are to optimise gain per unit length (for high frequency) and to increase operation temperature to the required 125oC while maintaining low current CW operation at 20 mW optical output power. This will be achieved by exploiting p type modulation doping in lasers and optimizing/combining nucleation layer, dislocation filter layer as well as thermal annealing. To increase the gain of the QD active region, P type modulation doping and high QD density are investigated in last 18 months and initial results are very promising.
Progress and Challenges
High performance InAs /GaAs QD devices have been demonstrated by growing on high quality GaAs/Si virtual substrates developed by exploiting new epitaxial growth technologies and new epitaxial structures in this WP. The detailed achievements are as following:
A InAs quantum dot photonic crystal cavity laser monolithically grown on on axis Si substrate 001 Top view and tilted cross section view SEM images of the fabricated PC cavity.
The laser spectrum shows the ground state emission at 1344 nm and excited state emission at 1277 nm, which has narrow linewidth of 0.43 nm and 1.39 nm, respectively
- The silicon based GaAs buffer layer with defect density <106/cm2 was successfully demonstrated by utilising InGaAs /GaAs superlattice layers and novel III-V nucleation layers on Si and Ge epi surface. Lasing up to 130 oC has been demonstrated for InAs /GaAs QD lasers grown on this high quality GaAs buffer on silicon substrates. To the best of our knowledge, this lasing operation temperature 130 oC is the highest operating temperature for lasers monolithically grown on silicon. To increase the gain of QD lasers, high density QD growth and p-type modulation doping have been studying in last 18 months. The high InAs /GaAs QD density of > 5.00×1010 cm2 was delivered for the purpose of the Hub. At the same time, p type modulation was extensively investigated by different designs The InAs /GaAs QD lasers with very short cavity of 0.333 mm was achieved with the best design so far The expertise on the design of p-type modulation doping for high gain QD laser devices, developed in this WP, is internationally leading.
- The antiphase boundary free III-V growth on complementary metal oxide semiconductor (CMOS) compatible on axis silicon 100 substrate is very important for the monolithic integration of III-V photonic materials and devices with the mature CMOS technology. The growth of III-V buffer on on axis silicon (100) substrates by MBE is developed by using UCL twin MBE system, in which group IV MBE growth chamber are connected with III-V growth chamber by an ultra high vacuum buffer chamber. The growth of Si epilayer is critical to annihilate antiphase boundaries for GaAs growth on silicon substrates, and the mechanism behind it is explained for first time. These results are proof of concepts and internationally leading
- Semiconductor Nano-Laser is very important for the next generation of Si based on chip optical interconnects III-V photonic crystal (PC) laser is regarded as a promising ultra compact light source with unique advantages of ultralow energy consumption and small footprint. Very recently, the first QD Photonic Crystal laser grown on silicon has been demonstrated as proof of concepts for Nano Lasers on Si. This work establishes a new route to form the basis of future monolithic light sources for high density optical interconnects in large scale silicon electronic and photonic integrated circuits. This result is world lead and was published at Nature Communications 11, 977 (2020).