InSb/InAs/InGa(Al)As/GaAs(0 0 1) metamorphic nanoheterostructures grown by MBE and emitting beyond 3 μm

Radiative versus non-radiative recombination in high-efficiency mid-IR InSb/InAs/In(Ga,Al)As/GaAs metamorphic nanoheterostructures

“…In this case a thick enough top region of the convex-graded MBL, possessing the strongly reduced TDs density, remains compressively strained with respect to the residual relaxed lattice parameter of the MBL. The thickness of the strained top MBL region depends on the grading profile used and seems to be the largest among all the implemented MBL profiles for the convex-graded one employed in this study [22]. X-ray diffraction rocking curves measured for the structures under study have revealed that the In 0.75 Al 0.25 As VS is almost fully unstrained at Δ = 6 mol.% [23].…”

“…Conventional solid source effusion cells were used to produce In, Ga, Al, and Sb 4 fluxes, whereas As 4 flux was supplied from a VAC-500 valved cracking cell. The real substrate temperature T S was measured by an IR pyrometer calibrated by using the wellknown temper atures of oxide desorption from the substrate surface and the (2 × 4)As-to-c(4 × 4)As surface reconstruction transition during GaAs buffer cooling under the As 4 flux, monitored in situ by reflection high energy electron diffraction (RHEED) [22].…”

“…Optimization of the convex-graded InAlAs MBL growth conditions included T S , growth rate, and As/III flux ratio. Originally we used low T S = 330-340 °C kept constant over the whole MBL growth, whereas the In mole fraction was increased just by variation of In flux intensity, which resulted in the strong growth rate enhancement (from 0.6 up to above 1.0 ML s −1 ) and non-reproducibly varied As/III ratio [22]. Contrary to that, in all the structures grown and studied in this work, the two stage T S variation was employed, starting with 375 °C for the first 200 nm of MBL and then reducing to 330 °C for the rest of MBL growth [27].…”

“…At P las higher than 10 mW, a saturation of both type dependences takes place. It should be noted also that in the structures under the study, the QW active region is located deeper from the surface than in the non-optimized one [22]. Therefore, to compare accurately the power dependences of the IQE in figure 3, we used the corrected excitation power P las for the non-optimized structure.…”

“…This paper is devoted to study of mid-IR PL and IQE versus structural quality and strain distribution in the metamorphic type-I InAs/InGaAs QWs with the type-II InSb sub-ML (⩽1 ML) insertions, grown by MBE on GaAs substrates by using a convex-graded InAlAs MBL [21]. The use of the convex-type MBL has been shown in our recent work [22] to provide a number of advantages over the linear one in achieving the lower TD density and smoother surface morphology. Here, we discuss the ways to surmount different non-radiative recombination processes by optimization of MBL growth conditions, detailed strain engineering in the metamorphic heterostructures, and optimization of their electronic band structure to achieve maximum IQE.…”