記住我
Here, we demonstrate the growth of emerging-APB-free GaSb layers on on-axis Si(001) via molecular beam epitaxy (MBE). A V-grooved structure is developed, leading to the annihilation of the APBs during the low/high-temperature GaSb layer depositions. In this paper, high-quality epitaxial GaSb films were grown on (111)-faceted-sawtooth Si(001) hollow substrates. The impact of ART on the large-scale growth and the uniformity of high-quality GaSb films on Si have been comprehensively investigated. The structural properties of morphology, crystalline quality, and optical properties have been characterized and discussed. These results are crucial to the fundamental study of Si-based GaSb for future optoelectronics and high-speed electronics.
An 8-in. Si(001) wafer was first patterned with U-shape grating structures along [110] direction by stepper and dry-etching. After cleaving the substrates into 10 × 10 mm2 dies and ex situ chemical cleaning for research purposes, the samples were loaded into IV-MBE for Si homoepitaxy to form a (111)-faceted hollow structure (Fig. 1). Then, they were transferred into III–V MBE in an ultra-high vacuum chamber having a base pressure lower than 1 × 10−9 mbar. The related procedures are in Table S1 and our previous works.2222. W. Q. Wei, J. Wang, B. Zhang, J. Zhang, H. Wang, Q. Feng, H. Xu, T. Wang, and J. J. Zhang, “ InAs QDs on (111)-faceted Si (001) hollow substrates with strong emission at 1300 nm and 1550 nm,” Appl. Phys. Lett. 113(5), 053107 (2018). https://doi.org/10.1063/1.5043169 A 400 nm low-temperature GaSb layer (360 °C, growth rate of 0.5 Å s−1, including 40 nm nucleation layer with V/III ratio of 6) and a 600 nm high-temperature layer (490 °C, growth rate of 1 Å s−1) were grown. Based on the initial buffer layer, InGaSb/GaSb quantum wells (QWs) as DFL separated by the 200 nm GaSb spacing layer were deposited. The DFL comprises 10 periods of 10 nm-In0.164Ga0.836Sb/10 nm-GaSb. The fluxes were measured using a Bayard–Alpert gauge before the growth (Fig. S1). Furthermore, pre-deposited GaAs/Si(001) templates were prepared as reference samples for direct comparison, commonly used for high-performance InAs/GaAs QD lasers on Si.14,2914. W. Q. Wei, J. Z. Huang, Z. Ji, D. Han, B. Yang, J. J. Chen, J. Qin, Y. Cui, Z. Wang, T. Wang, and J. J. Zhang, “ Reliable InAs quantum dot lasers grown on patterned Si (001) substrate with embedded hollow structures assisted thermal stress relaxation,” J. Phys. D: Appl. Phys. 55(40), 405105 (2022). https://doi.org/10.1088/1361-6463/ac843129. J. Z. Huang, W. Q. Wei, J. J. Chen, Z. Wang, T. Wang, and J. J. Zhang, “ P-doped 1300 nm InAs/GaAs quantum dot lasers directly grown on an SOI substrate,” Opt. Lett. 46(21), 5525 (2021). https://doi.org/10.1364/OL.437471Figures 2(a) and 2(c) show the cross-sectional scanning electron microscope (SEM) images of identical In0.164Ga0.836Sb/GaSb QWs deposited on the Si(001) and GaAs/Si(001), respectively. The corresponding backscattered electron (BSE) images are exhibited in Figs. 2(b) and 2(d), indicating the visible DFL structures with a sharp interface. Figure 2(e) displays a bright-field transmission electron microscope (TEM) image of the GaSb buffer directly grown on Si(001), taken along the [110] axis. A sawtooth-hollow-structure with Si homogeneous (111) facets is observed (highlighted by a red dotted line). Figures 2(f), 2(h), and 2(i) are the zoomed-in TEM images with different magnifications featuring the GaSb/Si interfaces. The conventional ART growth method often results in a rough Si surface after etching, which leads to a high defect density (109 cm−2) at the III–V/Si interface. To prevent these defects from propagating into the upper layer, tiara-like trapping structures are needed.3030. J. Z. Li, J. Bai, J.-S. Park, B. Adekore, K. Fox, M. Carroll, A. Lochtefeld, and Z. Shellenbarger, “ Defect reduction of GaAs epitaxy on Si (001) using selective aspect ratio trapping,” Appl. Phys. Lett. 91(2), 021114 (2007). https://doi.org/10.1063/1.2756165 Nevertheless, these structures are usually formed by chemical etching, which can introduce additional defects (such as pits and scratches) at the top of trapping structures. Homoepitaxially formed Si(111) facets obtained by our growth technology exhibit atomically smooth surfaces and sharp tips while effective for dislocation self-annihilation. Moreover, we can deposit GaSb in situ on the Si facets using our hybrid MBE technique, which avoids contamination and oxidation issues. Defects are mostly confined within 10 nm from the GaSb/Si interface. The APBs remain localized at the GaSb/Si interface without further propagation. Due to the significant lattice mismatch between GaSb and Si (12.2%), most defects with combined stacking faults (SFs) along the (111) plane are generated at the interface. However, attributed to the high symmetry and uniformity of homoepitaxially V-grooved structures, the defects lying along the two equivalent (111) planes [Fig. 2(h)] propagate and merge at the tip and then annihilate [Fig. 2(i)]. By comparing the results of III-V material grown on different kinds of V-grooved Si (for example, 113 planes), we concluded that the structure composed of (111) planes with high quality could more effectively reduce the defect density and capture defects at the III-V/Si interface. In addition, the Si homoepitaxy creates hollow structures that can alleviate thermal stress. According to our previous work,1414. W. Q. Wei, J. Z. Huang, Z. Ji, D. Han, B. Yang, J. J. Chen, J. Qin, Y. Cui, Z. Wang, T. Wang, and J. J. Zhang, “ Reliable InAs quantum dot lasers grown on patterned Si (001) substrate with embedded hollow structures assisted thermal stress relaxation,” J. Phys. D: Appl. Phys. 55(40), 405105 (2022). https://doi.org/10.1088/1361-6463/ac8431 the voids buried below the sawtooth structures can release the accumulative thermal stress of the III–V/Si system by decreasing the gap distance [d in Fig. 2(e)] between voids and the valley of the interface. The thermal stress release ratio can be reduced from 4.6% (d = 300 nm) to 9% (d = 0). It provides a reliable approach to growing and fabricating high-performance optoelectronic devices on Si without cracks.It is worth noting that the GaSb buffer was prepared by a two-step method. Here, a 40 nm thick low-temperature nucleation layer (360 °C and 0.5 Å s−1) can hinder the mobility of the deposited atoms leading to uniform coverage, annihilating the defect at the interface. A few point/planar defects still propagate along the growth direction, and they can be further suppressed by the III–V filter layers. Additionally, as shown in Fig. 2(g), the GaSb and Si can be distinguished from the film's selective area electron diffraction pattern, revealing a high-crystalline quality of the GaSb zinc blend structure. The temperature-dependent photoluminescence (PL) measurement of 1 μm thick GaSb/Si (V0, without DFL) is performed in Fig. 2(j). When the temperature increases from 4 to 300 K, the PL peak exhibits an evident redshift phenomenon, and the intensity decreases accordingly. At 4 K, the emission is dominated by a peak at ∼773 meV, usually seen in bulk GaSb,20,3120. T. Cerba, M. Martin, J. Moeyaert, S. David, J. L. Rouviere, L. Cerutti, R. Alcotte, J. B. Rodriguez, M. Bawedin, H. Boutry, F. Bassani, Y. Bogumilowicz, P. Gergaud, E. Tournié, and T. Baron, “ Anti phase boundary free GaSb layer grown on 300 mm (001)-Si substrate by metal organic chemical vapor deposition,” Thin Solid Films 645, 5–9 (2018). https://doi.org/10.1016/j.tsf.2017.10.02431. W. Jakowetz, W. Rühle, K. Breuninger, and M. Pilkuhn, “ Luminescence and photoconductivity of undoped p-GaSb,” Phys. Status Solidi A 12(1), 169–174 (1972). https://doi.org/10.1002/pssa.2210120117 which is also a solid indication of film quality. Our GaSb film consistently exhibits intense PL emission at low temperatures, relying on its low dislocation density through effective defect trapping from the patterned substrate. By increasing the temperature (≥77 K), the peak intensity begins to weaken, and the peak that appears as a shoulder of the 4 K emission near 714 meV vanishes because the band-to-band emission emerges, in good agreement with the literature.2020. T. Cerba, M. Martin, J. Moeyaert, S. David, J. L. Rouviere, L. Cerutti, R. Alcotte, J. B. Rodriguez, M. Bawedin, H. Boutry, F. Bassani, Y. Bogumilowicz, P. Gergaud, E. Tournié, and T. Baron, “ Anti phase boundary free GaSb layer grown on 300 mm (001)-Si substrate by metal organic chemical vapor deposition,” Thin Solid Films 645, 5–9 (2018). https://doi.org/10.1016/j.tsf.2017.10.024 PL emission is also observed when raised to room temperature, even without carrier confinement (for example, AlSb layers). The peak value near 720 meV corresponds to the GaSb bandgap (∼730 meV). Moreover, the full-width-at-half-maximum (FWHM) variation of the spectrum with temperature is summarized in Fig. 2(k). The FWHM value progressively increases from 27 meV at 4 K to 33.8 meV at 233 K while rising sharply to 44.7 meV at 300 K.Atomic force microscope (AFM) topographic images of GaSb surfaces under various structures are shown in Figs. 3 and S4. In the 5 × 5 μm2 scan area, the RMS roughness of the film surface is improved from ∼1 nm [V0, Fig. S4(a)] to 0.34 nm (V6, on Si) and 0.14 nm (G4, on GaAs/Si) by inserting InGaSb/GaSb DFL. Atomic steps and 2D terraces can be observed for each specimen, indicating high-crystalline quality. The local topographic profiles are presented in Fig. S5. The step height between adjoining terraces for all GaSb films is nearly 3 Å, corresponding to the size of a half unit-cell of single-crystalline bulk GaSb, which reveals a layer-by-layer growth. A more localized 2 × 2 μm2 scan is shown in Fig. S6. All films are atomically flat with low RMS roughness values between 0.1 and 0.2 nm. Moreover, 10 × 10 μm2 scans have been characterized. The surface RMS roughness of V6 is raised to ∼1 nm, and that of the film G4 is increased to 0.66 nm. From these relatively large areas, the TDDs of our GaSb films on Si and GaAs/Si are 1.2 × 107 and 6 × 106 cm−2, respectively (marked by white circles). To improve the accuracy, we conducted the electron channeling contrast imaging (ECCI) characterization for counting the TDs.11,3211. D. Jung, P. G. Callahan, and B. Shin, “ Low threading dislocation density GaAs growth on on-axis GaP/Si (001),” J. Appl. Phys. 122(22), 225703 (2017). https://doi.org/10.1063/1.500136032. D. Jung, J. Norman, M. J. Kennedy, C. Shang, B. Shin, Y. Wan, A. C. Gossard, and J. E. Bowers, “ High efficiency low threshold current 1.3 μm InAs quantum dot lasers on on-axis (001) GaP/Si,” Appl. Phys. Lett. 111(12), 122107 (2017). https://doi.org/10.1063/1.4993226 In addition, the SFs can be seen on the GaSb/Si in the 10 × 10 μm2 area. However, it is not visible for the GaSb/GaAs/Si attributed to the smaller in-plane lattice mismatch between GaSb and GaAs films (∼8.1%) and the complex GaAs buffer.2222. W. Q. Wei, J. Wang, B. Zhang, J. Zhang, H. Wang, Q. Feng, H. Xu, T. Wang, and J. J. Zhang, “ InAs QDs on (111)-faceted Si (001) hollow substrates with strong emission at 1300 nm and 1550 nm,” Appl. Phys. Lett. 113(5), 053107 (2018). https://doi.org/10.1063/1.5043169 The defects are mainly confined to the interfaces and tend to remain localized due to the buffer structures.Wide x-ray diffraction (XRD) 2θ/ω scans (20–80°) reveal only diffraction peaks corresponding to the reflections of the films and substrates (Fig. S7), indicating that no other-oriented phases than GaSb (001) are present in the epitaxial films. Figures 4(a)–4(c) show the 2θ/ω scans around the (004) reflections of GaSb films and the corresponding substrates. The presence of satellite peaks around the GaSb films' diffraction in Figs. 4(b) and 4(c) attests to the high-crystalline quality of InGaSb/GaSb DFL and abrupt interfaces. The extracted out-of-plane lattice parameter of the GaSb films is about 6.086–6.076 Å, close to the bulk lattice constant abulk = 6.096 Å, indicating full relaxation of the GaSb/Si film. The ω-scans measured for all the films around the GaSb(004) reflection are shown in the inset and Fig. S8. The mosaicity of the V0 is 0.085° (306 arc sec), which is further decreased to 0.07° (252 arc sec) by introducing InGaSb/GaSb DFL, in good agreement with the values found in the literature.18,2518. J. B. Rodriguez, K. Madiomanana, L. Cerutti, A. Castellano, and E. Tournié, “ X-ray diffraction study of GaSb grown by molecular beam epitaxy on silicon substrates,” J. Cryst. Growth 439, 33–39 (2016). https://doi.org/10.1016/j.jcrysgro.2016.01.00525. Q. Li, B. Lai, and K. M. Lau, “ Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer,” Appl. Phys. Lett. 111(17), 172103 (2017). https://doi.org/10.1063/1.5000100 For the GaSb/GaAs/Si film, the mosaicity is broadened to 0.152° (549 arc sec), probably due to the interdiffusion/intermixing of GaAs and GaSb. A Ga-rich surface was obtained before the GaSb growth during the thermal deoxidation because of the As-desorption, which caused the FWHM degradation.3333. M. T. H. Ha, S. H. Huynh, H. B. Do, C. T. Lee, Q. H. Luc, and E. Y. Chang, “ The effect of a Sb and Ga intermediate layer on the interfacial layer properties of epitaxial GaSb on GaAs grown by metalorganic chemical vapor deposition,” Thin Solid Films 669, 430–435 (2019). https://doi.org/10.1016/j.tsf.2018.10.056The in-plane lattice parameters (a) of GaSb films have been measured using XRD reciprocal space mapping (RSM) around the asymmetrical (-2–24) reflections, as depicted in Figs. 4(d)–4(f). Compared to the position of bulk GaSb (indicated by black triangles in the insets), the a of InGaSb/GaSb DFL tends to be enlarged because of the slight in-plane tension (∼1%) between In0.164Ga0.836Sb/GaSb epilayers. The short deviation is also due to the thermal expansion. There is a significant difference between the thermal expansion coefficients (Si: 2.6 × 10−6, GaAs: 5.73 × 10−6, and GaSb: 7.75 × 10−6 K−1). All GaSb films are in slightly compressive strain among (001) direction compared to the abulk because of the thermal expansion during the cooling temperature. For the G4 film, the node is elongated along the in-plane direction, which confirms the tendency extracted from the ω-scan in the inset of Fig. 4(c). The same behavior is observed around the symmetrical (004) reflection (Fig. S9). Furthermore, the elementary analysis has been performed for the G4 using energy dispersive x-ray spectroscopy (EDX, Fig. S10). The data show that some intermixing occurs at the GaSb/GaAs interface. Meanwhile, the In-desorption in InGaSb/GaSb and even in complex GaAs buffer is less expected and needs to be reduced in further work. This may be related to the desorption of residual In atoms from the chamber. Nevertheless, only a minimal amount of In is desorbed, leading to the slight enlargement of the a of our GaSb film.To further examine the film quality through heteroepitaxial growth on Si, ECCI characterizations are performed to evaluate the surface TDD (Figs. S11–S13). The results are shown in Fig. 5(a) and summarized in Tables I and II. The dislocation filtering efficiency is enhanced for a higher set of DFL. The initial GaSb film (V0) presents a TDD value of approximately 109 cm−2, in line with previously reported values in the literature.2020. T. Cerba, M. Martin, J. Moeyaert, S. David, J. L. Rouviere, L. Cerutti, R. Alcotte, J. B. Rodriguez, M. Bawedin, H. Boutry, F. Bassani, Y. Bogumilowicz, P. Gergaud, E. Tournié, and T. Baron, “ Anti phase boundary free GaSb layer grown on 300 mm (001)-Si substrate by metal organic chemical vapor deposition,” Thin Solid Films 645, 5–9 (2018). https://doi.org/10.1016/j.tsf.2017.10.024 After the introduction of InGaSb/GaSb DFL, the TDD is reduced to 4.2 × 108 cm−2 (V2), which is already improved from the value attained via GaInAsSb QWs (1 × 109 cm−2)1919. J. B. Rodriguez, L. Cerutti, G. Patriarche, L. Largeau, K. Madiomanana, and E. Tournié, “ Characterization of antimonide based material grown by molecular epitaxy on vicinal silicon substrates via a low temperature AlSb nucleation layer,” J. Cryst. Growth 477, 65–71 (2017). https://doi.org/10.1016/j.jcrysgro.2017.04.003 and in a good agreement with the value given by AlSb QDs layers (2.36 × 108 cm−2).2828. U. Serincan and B. Arpapay, “ Structural and optical characterization of GaSb on Si (001) grown by molecular beam epitaxy,” Semicond. Sci. Technol. 34(3), 035013 (2019). https://doi.org/10.1088/1361-6641/aafcbe The TDD is lowered by increasing filters to 3.5 × 107 cm−2 (V6). Meanwhile, GaSb/GaAs/Si film's TDD decreases from 3 × 109 (G1) to 2 × 107 cm−2 (G4). These decreases of nearly two orders of magnitude reveal that the TDs can be effectively reduced by InGaSb/GaSb QW filters. We also perform cryogenic PL experiments of GaSb/Si films with underneath DFLs [Fig. 5(b)]. At 77 K, QW DFLs bring an adjacent peak at a longer wavelength of 712 meV, which is probably generated by InGaSb layers. Meanwhile, the peak of GaSb is redshifted to 760 instead of 770 meV [Fig. 2(j)], which may be caused by the slight In-desorption. A similar shift has been observed at room temperature (Fig. S14). Moreover, the integrated intensity in Fig. 5(c) is gradually enhanced by reducing TDD. Compared to the V0 film, both the peak intensity value and the integrated intensity of the sample V6 are enhanced by 27.3% and 34.5%, respectively, which would help improve the performance of GaSb-based infrared devices on Si. In addition, the mosaicity variation of GaSb films exhibits an opposite tendency, which matches the ECCI results. Although the transport properties of GaSb films would require further investigations (for instance, Hall mobility), our experimental results present a robust basis and already show the critical impact of homoepitaxial V-grooved Si and InGaSb/GaSb DFL on morphology and crystalline quality, which is of high interest for Si-based antimonide applications.
TABLE I. Summary of the sample, number of DFL, thickness, TDD, and AFM-RMS roughness.
FilmNo.DFL numberThickness (μm)TDD (cm−2)AFM roughness 5 × 5 μm2 (nm)GaSb/SiV001.069.5 × 1080.918V102.258.6 × 1080.716V211.054.2 × 1080.545V321.613 × 1080.529V442.549.3 × 1070.477V563.556 × 1070.401V694.913.5 × 1070.34GaSb/GaAs/SiG100.453 × 1090.499G221.55.5 × 1080.291G353.122.7 × 1070.23G484.612 × 1070.14TABLE II. Summary of literature data about the structural properties of GaSb/Si films.
Ref.MethodThickness (μm)Mosaicity (arc sec) ω-scanNormalized mosaicity34,3534. V. M. Kaganer, R. Köhler, M. Schmidbauer, R. Opitz, and B. Jenichen, “ X-ray diffraction peaks due to misfit dislocations in heteroepitaxial structures,” Phys. Rev. B 55(3), 1793–1810 (1997). https://doi.org/10.1103/PhysRevB.55.179335. C. J. K. Richardson, L. He, and S. Kanakaraju, “ Metamorphic growth of III-V semiconductor bicrystals,” J. Vac. Sci. Technol. B 29(3), 03C126 (2011). https://doi.org/10.1116/1.3565436AFM roughness (nm)TDD (cm−2)2525. Q. Li, B. Lai, and K. M. Lau, “ Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer,” Appl. Phys. Lett. 111(17), 172103 (2017). https://doi.org/10.1063/1.5000100MOCVD0.156500.085.4 (5 × 5 μm2)⋯13000.095⋯⋯2424. M. Baryshnikova, Y. Mols, Y. Ishii, R. Alcotte, H. Han, T. Hantschel, O. Richard, M. Pantouvaki, J. Van Campenhout, D. Van Thourhout, R. Langer, and B. Kunert, “ Nano-ridge engineering of GaSb for the integration of InAs/GaSb heterostructures on 300 mm (001) Si,” Crystals 10(4), 330 (2020). https://doi.org/10.3390/cryst10040330MOVPE0.3⋯⋯⋯2 × 1092727. Y. K. Noh, “ Growth of low defect AlGaSb films on Si (100) using AlSb and InSb quantum dots intermediate layers,” J. Cryst. Growth 323(1), 405–408 (2011). https://doi.org/10.1016/j.jcrysgro.2011.01.027MOCVD12280.0731.5 (5 × 5 μm2)⋯2020. T. Cerba, M. Martin, J. Moeyaert, S. David, J. L. Rouviere, L. Cerutti, R. Alcotte, J. B. Rodriguez, M. Bawedin, H. Boutry, F. Bassani, Y. Bogumilowicz, P. Gergaud, E. Tournié, and T. Baron, “ Anti phase boundary free GaSb layer grown on 300 mm (001)-Si substrate by metal organic chemical vapor deposition,” Thin Solid Films 645, 5–9 (2018). https://doi.org/10.1016/j.tsf.2017.10.024MBE0.258000.1270.6 (5 × 5 μm2)1 × 10100.92500.0750.4 (5 × 5 μm2)8 × 1081919. J. B. Rodriguez, L. Cerutti, G. Patriarche, L. Largeau, K. Madiomanana, and E. Tournié, “ Characterization of antimonide based material grown by molecular epitaxy on vicinal silicon substrates via a low temperature AlSb nucleation layer,” J. Cryst. Growth 477, 65–71 (2017). https://doi.org/10.1016/j.jcrysgro.2017.04.003MBE16600.212.2 (5 × 5 μm2)1 × 1092828. U. Serincan and B. Arpapay, “ Structural and optical characterization of GaSb on Si (001) grown by molecular beam epitaxy,” Semicond. Sci. Technol. 34(3), 035013 (2019). https://doi.org/10.1088/1361-6641/aafcbeMBE12600.0831.2 (10 × 10 μm2)2.36 × 108This workMBE1.055250.1710.545 (5 × 5 μm2)4.2 × 1084.912520.1781.07 (10 × 10 μm2)3.5 × 107In conclusion, high-quality epitaxial GaSb films were achieved by MBE direct epitaxial growth on both on-axis Si(001) and GaAs/Si(001). The structural and optical properties of the samples are comprehensively characterized. Despite the significant lattice mismatch, all the films crystallize in the zinc blend structure with (001)-orientation while remaining APB-free and atomically flat. By introducing (111)-faceted Si hollow structure with InGaSb/GaSb DFL, the surface RMS roughness achieved for the GaSb film on Si reached the lowest value to date, with a value of 0.34 nm on Si(001) and 0.14 nm on GaAs/Si(001). Moreover, the low mosaicity of the GaSb(004) reflection is 252 arc sec (on Si) and doubled to 549 arc sec (on ∼2 μm thick GaAs/Si metamorphic platform), probably due to the interdiffusion between GaSb and GaAs. It is worth noting that the TDD of the GaSb/GaAs/Si film is reduced to 2 × 107 cm−2, which is at least one order of magnitude lower than the minimum value found in the literature (∼2.4 × 108 cm−2). Regardless of a slightly higher TDD of 3.5 × 107 cm−2, the GaSb film directly grown on Si(001) would have significant advantages over GaSb/GaAs/Si, such as a relatively simple growth process, arsenic-free, and thinner buffer structures. The III–V/IV hybrid growth method implemented here can potentially be directly transferred onto 300 mm CMOS-compatible silicon wafers, which opens up the way for integrating antimony-based semiconductors at a large scale for optoelectronic or high-speed electronic devices.
留言 (0)