Realization of high-quality InGaAs/GaAs quantum dot growth on Ge substrate and improvement of optical property through ex-situ ion implantation (original) (raw)
Related papers
Technical Physics Letters, 2002
The optical and structural properties of heterostructures with quantum dots (QDs) in the InAs/GaAs system overgrown with an InGaAs solid solution were studied. The QD layers were obtained using different molecular beam deposition techniques: molecular beam epitaxy versus submonolayer migration-stimulated epitaxy. The photoluminescence peaks in the spectra of samples with overgrown QD layers occur in the wavelength range from 1.18 to 1.32 µ m. It was found that the growth conditions also influence the electronic structure of QDs.
Journal of Materials Science: Materials in Electronics, 2017
[6] and tunneling diodes [7]. It was shown that the disadvantages of InAs/GaAs or InAs/InGaAs QD systems are connected with QD non-homogeneous surface distribution, significant dispersion of QD sizes or QD compositions that lead to the differences in optical device parameters [8-10]. Additional factor that has an impact on QD device parameters is the In/Ga atom inter-diffusion between the QDs and QWs. In/Ga intermixing can be realized on the different stages of QD and QW growth processes. A number of papers were published recently concerning the study of In/Ga intermixing at thermal annealing [11-13]. The main attention in these papers was connected with the spectral shift investigation for QD emission that was detected after thermal annealing. However the essentially more information concerning In/Ga intermixing between QDs and QW can be obtained at the joint investigation of QD emission and QW parameters using high-resolution X ray diffraction (HR-XRD) method [14, 15]. In present paper the emission and HR-XRD were studied in InGaAs/GaAs QW structures with embedded InAs QDs grown at different temperatures from the range 470-535 °C. 2 Experimental conditions InAs QD structures were grown by the molecular beam epitaxy (MBE) on the (001) semi-insulating GaAs substrates. Each structure includes a 200 nm GaAs buffer layer and a 100 nm GaAs upper final capping layer that were grown at 600 °C (Fig. 1). Between GaAs layers there are a second In 0.15 Ga 0.85 As buffer layer (2 nm), then the self-organized InAs QD array formed by the deposition of 2.4 ML of InAs, and first capping In 0.15 Ga 0.85 As layers (Fig. 1). Both the buffer and capping In 0.15 Ga 0.85 As layers were grown at 510 °C. The growth temperature of InAs QDs varies for Abstract GaAs/In 0.15 Ga 0.85 As/GaAs QWs with embedded InAs QDs grown at different temperatures have been studied by means of the photoluminescence (PL), X ray diffraction (XRD) and high resolution XRD (HR-XRD) methods. PL study has detected varying of QD parameters and HR-XRD permits monitoring the QW parameters. It is shown that increasing the QD growth temperature up to 510 °C leads to raising the QD sizes, to shift of QD emission peak to low energy and increasing the PL intensity of QDs. Simultaneously Ga/In atom intermixing is realized mainly between the InGaAs buffer and InAs wetting layers and did not influent on the InAs QD composition. At higher QD growth temperatures (525-535 °C) the PL intensity of QDs decreases significantly together with decreasing the QD heights and the shift of PL peaks into higher energy. Fitting the HR-XRD results has revealed that Ga/In atom intermixing involves the composition changes in buffer and wetting layers, as well as in QDs. The mentioned optical and structural effects have been discussed in details.
Journal of Physics: Conference Series, 2019
The development of GaAs/Si heterostructures can be an important stage for use as solar cells, LEDs and lasers based on silicon substrates. At present, A3B5 compounds grown epitaxial on Si substrates are of great interest because of the monolithic integration of optoelectronic devices with Si-based microelectronics. High-quality epitaxial growth of heterostructures will not only ensure high mobility of the carrier materials, but also preserve the advantages of lightweight and inexpensive Si substrates with high mechanical strength and excellent thermal parameters. However, obtaining A3B5 compounds with high quality crystals of GaAs/Si heterostructures is a difficult task due to the formation of an antiphase domain boundary as a result of the growth of polar GaAs on a non-polar Si substrate. Because of this, a high density of penetrating dislocations arises due to the mismatch of the lattice parameters (4.1%), as well as the coefficient of thermal expansion (62%).
Emission and HR-XRD varying in GaAs/AlGaInAs heterostructures with InAs quantum dots at annealing
Journal of Materials Science: Materials in Electronics, 2020
GaAs/Al 0.30 Ga 0.70 As/AlGaInAs/ heterostructures grown by molecular beam epitaxy with embedded InAs quantum dots (QDs) have been investigated before and after thermal annealing at 640 °C for 2 h. Two types of QD structures with the different compositions of capping layers: (Al 0.30 Ga 0.70 As (#1) and Al 0.10 Ga 0.75 In 0.15 As (#2)), are studied using the photoluminescence (PL), X-ray diffraction (XRD) and high-resolution XRD (HR-XRD) techniques. The high PL intensity, smaller half width of PL bands and lower energy of the ground state (GS) emission are detected in the structure with the Al 0.10 Ga 0.75 In 0.15 As capping layer. The blue shift of PL spectra is detected after annealing and this shift is more significant in the structure with Al 0.10 Ga 0.75 In 0.15 As capping as well. The last effect has been explained by the efficient Ga/In inter-diffusion at the AlGaInAs/ InAs QD interface in #2 owing to the smaller In-As binding energy in comparison with Al-As and Ga-As ones in the studied alloy. The composition variation of the QDs and quantum wells (QWs) due to Ga/In intermixing at annealing has been modeled on the base of the numerical simulation of HR-XRD scans with the help of X′ Pert Epitaxy software.
Epitaxial growth of quantum-dot heterostructures on metamorphic buffers
2005
Recent achievements in self-organized quantum dots (QDs) have demonstrated their potential for long-wavelength laser applications. However, the wavelength of QD structures pseudomorphically grown on GaAs substrate is typically not longer than 1 .3 tm. In this work we study a novel approach for extension of the spectral range of GaAs-based diode lasers up to 1.5 jtm. We use a sensitivity of QD emission to the band gap energy of surrounding matrix. The method is based on formation of a QD array inside a metamorphic InGaAs epilayer. Growth regimes of metamorphic buffer that enable mirror-like surface morphology in combination with effective dislocation trapping are discussed. Structural and optical properties of metamorphic InAs/InGaAs QDs are presented. It is shown that the wavelength of QD emission can be controllably tuned in the 1.37-1.58 tm range by varying the composition of metamorphic InGaAs matrix. Details of formation, fabrication, and characterization of metamorphic-based diode lasers are also presented. We demonstrate a lasing wavelength as long as 1.48 jtm in the 20-80 °C temperature interval. The minimum threshold current density is 800 A/cm2 at RT. The external differential efficiency and pulsed power maximum exceed 50%and 7 W, respectively.
Quantum dot integration in heterostructure solar cells
Solar Energy Materials and Solar Cells, 2006
InAs self-assembled quantum dots (SA-QDs) were incorporated into GaAlAs/GaAs heterostructure for solar cell applications. The structure was fabricated by molecular beam epitaxy on p-GaAs substrate. After the growth of GaAs buffer layer, multi-stacked InAs QDs were grown by self-assembly with a slow growth rate of 0.01 ML/s, which provides high dot quality and large dot size. Then, the structure was capped with n-GaAs and wide band gap n-GaAlAs was introduced. One, two or three stacks of QDs were sandwiched in the p-n heterojunction. The contribution of QDs in solar cell hetero-structure is the quantized nature and a high density of quantized states. I-V characterization was conducted in the dark and under AM1 illumination with 100 mW/cm 2 light power density to confirm the solar cell performance. Photocurrent from the QDs was confirmed by spectral response measurement using a filtered light source (1.1-mm wavelength) and a tungsten halogen lamp with monochromator with standard lock-in technique. These experimental results indicate that QDs could be an effective part of solar cell heterostructure. A typical I-V characteristic of this yet-to-be-optimized solar cell, with an active area of 7.25 mm 2 , shows an open circuit voltage V oc of 0.7 V, a short circuit current I sc of 3.7 mA, and a fill factor FF of 0.69, leading to an efficiency Z of 24.6% (active area).
Nanotechnology, 2006
We systematically investigated the correlation between morphological and optical properties of InGaAs self-assembled quantum dots (QDs) grown by solid-source molecular beam epitaxy on GaAs (n11)B (n = 9, 8, 7, 5, 3, 2) substrates. Remarkably, all InGaAs QDs on GaAs(n11)B under investigation show optical properties superior to those for ones on GaAs(100) as regards the photoluminescence (PL) linewidth and intensity. The morphology for growth of InGaAs QDs on GaAs (n11)B, where n = 9, 8, 7, 5, is observed to have a rounded shape with a higher degree of lateral ordering than that on GaAs(100). The optical property and the lateral ordering are best for QDs grown on a (511)B substrate surface, giving a strong correlation between lateral ordering and PL optical quality. Our results demonstrate the potential for high quality InGaAs QDs on GaAs(n11)B for optoelectronic applications.
Direct Heteroepitaxy and Selective Area Growth of GaP and GaAs on Si by Hydride Vapor Phase Epitaxy
physica status solidi (a), 2020
Direct heteroepitaxy and selective area growth (SAG) of GaP and GaAs on Si(100) and Si(111) are implemented by low-pressure hydride vapor phase epitaxy (LP-HVPE), which are facilitated by buffer layers grown at 410-490 C with reactive gas mixing directly above Si substrates. High-density islands observed on GaP buffer layers on Si result in rough morphology and defect formation in the subsequent GaP layers grown at 715 C. The impact of growth temperature of GaAs buffer layers on the crystal quality of GaAs/Si is studied. A decreased nucleation temperature significantly improves the morphology and crystalline quality of the overall GaAs growth on Si. It is observed that Si(111) substrates are favorable for both GaP and GaAs growths in comparison with Si(100). In SAGs of GaP/Si and GaAs/Si, the high selectivity innate to HVPE is maintained in the used unconventional growth regime. The spatially resolved photoluminescence mapping reveals the material quality of GaAs/Si is enhanced by defect filtering by SAG. The outcomes of this work will pave the way of III-V/Si integration realized by cost-effective HVPE for photonic device applications.