Growth and properties of the self‐catalyzed heterostructured GaP nanowires (NWs) with GaP1 − xAsx insertions in the form of nanodiscs (NDs) grown by means of molecular‐beam epitaxy on Si (111) substrate are studied. To obtain the NDs with the different composition and optoelectronic properties, the ratio of As and P fluxes is varied. Structural properties of the synthesized heterostructures are characterized by means of transmission electron microscopy. Energy dispersive X‐ray spectroscopy is used to study chemical composition of the NDs. The maximum achieved fraction x in the NDs is nearly 60%. Sublinear dependence of As concentration in the ND on the As/P flux ratio is observed and theoretical description for the observed phenomenon is provided. The proposed model can be used to estimate the predicted As/P ratio for the synthesis of GaPAs NDs as well as NWs of the required composition. Microphotoluminescence (μPL) studies demonstrate the appearance of broadband PL signal in the spectral range between 600 and 700 nm, corresponding to the NDs with different compositions. Spectra intensity modulation is found due to longitudinal Fabry–Pérot‐type resonances in the individual NWs.
GaN nanowires were grown using selective area plasma-assisted molecular beam epitaxy on SiOx/Si(111) substrates patterned with microsphere lithography. For the first time, the temperature–Ga/N2 flux ratio map was established for selective area epitaxy of GaN nanowires. It is shown that the growth selectivity for GaN nanowires without any parasitic growth on a silica mask can be obtained in a relatively narrow range of substrate temperatures and Ga/N2 flux ratios. A model was developed that explains the selective growth range, which appeared to be highly sensitive to the growth temperature and Ga flux, as well as to the radius and pitch of the patterned pinholes. High crystal quality in the GaN nanowires was confirmed through low-temperature photoluminescence measurements.
High-performance injection microdisk lasers grown on Si substrate are demonstrated for the first time. Continuous wave lasing in microlasers with diameters from 14 to 30 µm is achieved at room temperature. The minimal threshold current density of 600 A/cm 2 (room temperature, continuous wave regime, heatsink-free uncooled operation) is comparable to that of high-quality microdisk lasers on GaAs substrates. Microlasers on silicon emit in the wavelength range of 1320-1350 nm via the ground state transition of InAs/InGaAs/GaAs quantum dots. High stability of the lasing wavelength (dλ/dI=0.1 nm/mA) and low specific thermal resistance of 4×10 -3 о С×cm 2 /W are demonstrated. © 2017 Optical Society of AmericaOCIS codes : (140.5960 Semiconductor lasers; (140.3945 Microcavities).http://dx.doi.org/10.1364/OL.99.099999Realization of compact silicon-based lasers capable for reliable operation at elevated temperatures is a subject of persistent attempts of many research groups worldwide. To date, several approaches have been proposed to realize light source on silicon. This includes the hybrid III-V-silicon integration, that can be done using different bonding techniques such as flip-chip bonding [1] or molecular bonding [2,3]. For this purpose, InP-based laser structures with InAsP/InGaAsP quantum wells (QWs) were used. The highest operation temperature for InP-based microring lasers with a diameter of 50 μm is 65 o C[4]. For further increase of the operating temperature (up to 105C) a special thermal shunt design improving thermal conductivity is required [5]. The highest operating temperature of InP-based microlasers is limited by small energy of the carrier confinement in the active region (small conduction band offsets). Moreover, it is often in bonded structures that the major part of the optical field is located in the silicon waveguide and its overlap with the III-V active region is only a few percents. Another group of integration methods is based on direct epitaxial growth of III-V active layers on silicon substrates. An approach based on Ge/Si (001) virtual substrate [6] has been recently used to achieve room-temperature lasing in InGaAs/GaAs quantum well microdisk (MD) lasers with 23 µm diameter [7]. The minimal threshold current density was 28 kA/cm 2 reflecting a high sensitivity of a quantum well active region to various defects originated from both epitaxial growth on silicon and damaged microresonator sidewalls. In this respect quantum dots (QDs) can offer advantageous characteristics owing to a suppressed lateral transport of charge carriers which prevents their diffusion towards non-radiate recombination centers. Owing to this unique property of QDs, a significant progress has been demonstrated in the past years in realization of III-V-Si injection lasers [8][9][10]. A low density of threading dislocations on the order of 10 5 cm −2 in the III-V epilayers grown on silicon (100)-oriented substrates with 4 o offcut is achieved by combining a nucleation layer and dislocation filter layers with in situ ther...
In the present work we report on the optimization of MBE growth conditions and design of metamorphic In(Al)(Ga)As/GaAs heterostructures. This results in a strong decrease in the density of threading dislocations in the upper (active) layers and the improvement of surface morphology. Room-temperature mobility in metamorphic modulation-doped InGaAs/InAlAs heterostructures was 8100 cm2 V−1 s−1, which is comparable to that of InP-based structures and noticeably superior to pseudomorphic GaAs-based structures. InAs quantum dots formed in a metamorphic InGaAs matrix on a GaAs substrate were used for lasers with promising characteristics (emitting wavelengths of 1.46 µm, with threshold current densities of 1.4 kA cm−2).
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