Co-doped 1.3μm InAs Quantum Dot Lasers with high gain and low threshold current

The mechanism by which co-doping reduces threshold current in O-band Quantum dot lasers is examined, with n-type direct doping of the dots reducing threshold current and p-type modulation doping improving the temperature dependence of threshold current density, relative to undoped samples

Electron transport lifetimes in InSb/Al1-xInxSb quantum well 2DEGs

We report magnetotransport measurements of InSb/Al1-xInxSb modulation doped quantum well (QW) structures and the extracted transport ( ) tt and quantum (tq) lifetime of carriers at low temperature (<2K.) We consider conventional transport lifetimes over a range of samples with different doping levels and carrier densities, and deduce different transport regimes dependent on QW state filling calculated from self-consistent Schrödinger–Poisson modelling. For samples where only the lowest QW subband is occupied at electron densities of 2.13 10 ´ 11 cm−2 and 2.54 10 ´ 11 cm−2 quantum lifetimes of tq » 0.107 ps, and tq » 0.103 ps are extracted from Shubnikov–de Haas oscillations below a magnetic field of 0.8 T. The extracted ratios of transport to quantum lifetimes, t t t q » 17 and t t t q » 20 are similar to values reported in other binary QW two-dimensional electron gas systems, but are inconsistent with predictions from transport modelling which assumes that remote ionized donors are the dominant scattering mechanism. We find the low t t t q ratio and the variation in transport mobility with carrier density cannot be explained by reasonable levels of background impurities or well width fluctuations. Thus, there is at least one additional scattering mechanism unaccounted for, most likely arising from structural defects

1.3-μm InAs Quantum Dot Lasers with P-type modulation and direct N-type co-doping

O-band quantum dot lasers with co-doping reduce threshold current density relative to the undoped case, for 1mm long uncoated lasers from 245Acm-2 to 132Acm-2 at 27°C and 731Acm-2 to 312Acm-2 at 97°C. Improvements are also significant compared to lasers employing any one doping strategy

Degradation of III–V Quantum Dot Lasers Grown Directly on Silicon Substrates

Initial age-related degradation mechanisms for InAs quantum dot lasers grown on silicon substrates emitting at 1.3 μm are investigated. The rate of degradation is observed to increase for devices operated at higher carrier densities and is therefore dependent on gain requirement or cavity length. While carrier localization in quantum dots minimizes degradation, an increase in the number of defects in the early stages of aging can increase the internal optical-loss that can initiate rapid degradation of laser performance due to the rise in threshold carrier density. Population of the two-dimensional states is considered the major factor for determining the rate of degradation, which can be significant for lasers requiring high threshold carrier densities. This is demonstrated by operating lasers of different cavity lengths with a constant current and measuring the change in threshold current at regular intervals. A segmented-contact device, which can be used to measure the modal absorption and also operate as a laser, is used to determine how the internal optical-loss changes in the early stages of degradation. Structures grown on silicon show an increase in internal optical loss, whereas the same structure grown on GaAs shows no signs of increase in internal optical loss when operated under the same conditions