We demonstrate a GaAs based Quantum Dot (QD) optoelectronic integration platform with results for surface grating couplers (SGC) and edge emitting lasers. SGCs usually perform poorly in systems without a large refractive index contrast and here we utilize thin oxidized Al0.98Ga0.02As layers to overcome this issue. The results show an increase from 10% to 30% in surface grating coupling efficiency, for the unoxidized compared to oxidized, and substrate-loss decrease from 70% to 20%. Electrically pumped edge-emitting lasers on the same platform exhibit comparable performance to more standard 1300nm QD designs. We describe the design, fabrication and characterization of these devices.
We introduce direct n-doping of quantum dots together with modulation p-doping as a technique to reduce both the threshold current density and the temperature dependence of threshold current density in 1.3um emitting quantum dot lasers. Threshold current density in 1mm long QD lasers with cleaved and uncoated facets is effectively halved at both 27°C and at 97°C when using co-doping as compared to the undoped case. Results indicate that modulation p-doping can improve the threshold current temperature dependence and direct n-doping reduces the magnitude of threshold current density and that the benefits of each is maintained when used together.
The performance of O-band InAs/GaAs quantum-dot (QD) lasers grown by molecular beam epitaxy with three different doping strategies are investigated in a temperature range 17 °C – 97 °C. We demonstrate lasers with a reduced threshold current using direct n-doping (during the dot formation) in the active region compared lasers with a nominally undoped active region. We explain results using calculations of the dot and wetting layer potentials and the electron and hole energy levels.
Monolithic integration of III–V materials and devices on CMOS compatible on‐axis Si (001) substrates enables a route of low‐cost and high‐density Si‐based photonic integrated circuits. Inversion boundaries (IBs) are defects that arise from the interface between III–V materials and Si, which significantly lowers the quality of III–V materials on Si. Here, a novel technique to achieve IB‐free GaAs monolithically grown on on‐axis Si (001) substrates by realizing the alternating straight and meandering single atomic steps on Si surface has been introduced via all-molecular beam epitaxy approach without the use of double Si atomic steps, which was previously believed to be the key for IB‐free III–V growth on Si. The periodic straight and meandering single atomic steps on Si surface are results of high‐temperature annealing of Si buffer layer. As a demonstration, an electrically pumped InAs quantum‐dot laser has been fabricated based on this IB‐free GaAs/Si platform with a maximum operating temperature of 120 °C. These results can be a major step towards monolithic integration of III–V materials and devices with the mature CMOS technology.
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