Search Results (40)

The integration of thick homoepitaxial layers on silicon carbide (SiC) substrates is critical for enabling high-voltage power devices, yet it remains challenged by substrate surface quality and wafer geometry evolution. This study investigates the relationship between substrate preparation—particularly chemical mechanical planarization (CMP)—and the impact on wafer bow, total thickness variation (TTV), local thickness variation (LTV), and defect propagation during epitaxial growth. Seven 150 mm, 4° off-axis, prime-grade 4H-SiC substrates from a single ingot were processed under high-volume manufacturing (HVM) conditions and grown with epitaxial layers ranging from 12 μm to 100 μm. Metrology revealed a strong correlation between increasing epitaxial thickness and geometric deformation, especially beyond 31 μm. Despite initial surface scratches from CMP, hydrogen etching and buffer layer deposition significantly mitigated scratch propagation, as confirmed through defect mapping and SEM/FIB analysis. These findings provide a deeper understanding of the substrate-to-epitaxy integration process and offer pathways to improve manufacturability and yield in thick-epilayer SiC device fabrication. Full article

The precise fabrication of semiconductor-based photonic crystals with tailored optical properties is critical for advancing photonic devices. GaP(111) is a material of particular interest due to its high refractive index, wide optical bandgap, and pronounced optical anisotropy, offering unique opportunities for photonic applications. Its near-lattice matching with silicon substrates further facilitates integration with existing silicon-based technologies. In this study, we present the growth of high-quality GaP(111) thin films using gas-source molecular-beam epitaxy (GSMBE), achieving atomically smooth terraces for the homo-epitaxy of GaP(111). We demonstrate the fabrication of photonic crystal cavities from GaP(111), employing AlGaP(111) as a sacrificial layer, and achieve a quality factor of 1200 for the cavity mode with resonance around 1500 nm. This work highlights the potential of GaP(111) for advanced photonic architectures, particularly in applications requiring strong light confinement and nonlinear optical processes, such as second-harmonic and sum-frequency generation. Full article

Epitaxial growth can be used to guide the controllable growth of one metal on the surface of another substrate by matching the interface lattice, thus improving the dendrite tendency of metal growth. The atomic arrangement of the Cu (111) crystal plane of the FCC structure is similar to that of the Zn (0002) crystal plane of the HCP structure, which is theoretically expected to promote the heterogeneous epitaxial nucleation growth of metal zinc under low strain. In this paper, the molecular dynamics method is used to simulate the atomic process of zinc film growth on the Cu (111) surface. It is found that the behavior of zinc-adsorbed atoms on the substrate surface conforms to the epitaxial growth mode. The close-packed structure grown along the (0002) direction of the layered clusters is tiled on the Cu (111) surface, forming a highly ordered low-lattice-mismatch interface. When a large area of layered zinc clusters cover the substrate, the growth mode will change from heteroepitaxial growth to homoepitaxial growth of Zn atoms on the zinc film, forming a lamellar distribution composed of FCC and HCP structure grains. Polycrystalline zinc film with a planar structure with a (0002) surface preferred a crystal plane. The increase in incident energy is helpful in improving the quality of zinc films, while the deposition rate, corresponding to the deposition temperature and electrolyte ion concentration, has no significant effect on the surface morphology and crystal structure of single metal films. In summary, the atomic arrangement of the Cu (111) surface has a strong guiding effect on the atomic ordered arrangement in the zinc film crystal, which is suitable for the epitaxial deposition of the substrate to induce the ordered growth of the Zn (0002) crystal plane. Full article

With the development of diamond technology, its application in the field of electronics has become a new research hotspot. Hydrogen-terminated diamond has the electrical properties of P-type conduction due to the formation of two-dimensional hole gas (2DHG) on its surface. However, due to various scattering mechanisms on the surface, its carrier mobility is limited to 50–200 cm²/(Vs). In this paper, the effects of process parameters (temperature, CH₄ concentration, time) on the electrical properties of hydrogen-terminated diamond were studied by microwave plasma chemical vapor deposition (CVD) technology, and hydrogen-terminated diamond with a high carrier mobility was obtained. The results show that homoepitaxial growth of a diamond film on a diamond substrate can improve the carrier mobility. Hydrogen-terminated diamond with a high carrier mobility and low sheet resistance can be obtained by homoepitaxial growth of a high-quality diamond film on a diamond substrate with 4% CH₄ concentration and hydrogen plasma treatment at 900 ℃ for 30 min. When the carrier concentration is 2.03 × 10¹²/cm², the carrier mobility is 395 cm²/(Vs), and the sheet resistance is 7.82 kΩ/square, which greatly improves the electrical properties of hydrogen-terminated diamond. It can enhance the transmission characteristics of carriers in the conductive channel, and is expected to become a potential material for application in devices, providing a material choice for its application in the field of semiconductor devices. Full article

The gypsum crystals (CaSO₄·2H₂O) crystallizes in a low symmetry system (monoclinic) and shows a marked layered structure along with a perfect cleavage parallel to the {010} faces. Owing to its widespread occurrence, as a single or twinned crystal, here the gypsum equilibrium (E.S.) and growth shapes (G.S.) have been re-visited. In making the distinction among E.S. and G.S., in the present work, the basic difference between epitaxy and homo-taxy is clearly evidenced. Gypsum has also been a fruitful occasion to recollect the general rules concerning either contact or penetration twins, for free growing and for twinned crystals nucleating onto pre-existing substrates. Both geometric and crystal growth aspects have been considered as well, by unifying theory and experiments of crystallography and crystal growth through the intervention of ${\mathsf{\beta }}_{\mathrm{adh}}$, the physical quantity representing the specific adhesion energy between gypsum and other phases. Hence, the adhesion energy allowed us to systematically use the Dupré’s formula. In the final part of the paper, peculiar attention has been paid to sediments (or solution growth) where the crystal size is very small, in order to offer a new simple way to afford classical (CNT) and non-classical nucleation (NCNT) theories, both ruling two quantities commonly used in the industrial crystallization: the total induction times (${\mathrm{t}}_{\mathrm{i}\mathrm{n}\mathrm{d}}^{\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}$) and crystal size distribution (CSD). Full article

In this study, we systematically explore the impact of C/Si ratio, pre-carbonization time, H₂ etching time, and growth pressure on the buffer layer and subsequent epitaxial layer of 6-inch 4H-SiC wafers. Our findings indicate that the buffer layer’s C/Si ratio and growth pressure significantly influence the overall quality of the epitaxial wafer. Specifically, an optimal C/Si ratio of 0.5 and a growth pressure of 70 Torr yield higher-quality epitaxial layers. Additionally, the pre-carbonization time and H₂ etching time primarily affect the uniformity and surface quality of the epitaxial wafer, with a pre-carbonization time of 3 s and an H₂ etching time of 3 min found to enhance the surface quality of the epitaxial layer. Full article

To address surface morphological defects that have a destructive effect on the epitaxial wafer from the aspect of 4H-SiC epitaxial growth, this study thoroughly examined many key factors that affect the density of defects in 4H-SiC epitaxial wafer, including the ratio of carbon to silicon, growth time, application of a buffer layer, hydrogen etching and other process parameters. Through systematic experimental verification and data analysis, it was verified that when the carbon–silicon ratio was accurately controlled at 0.72, the density of defects in the epitaxial wafer was the lowest, and its surface flatness showed the best state. In addition, it was found that the growth of the buffer layer under specific conditions could effectively reduce defects, especially surface morphology defects. This provides a new idea and method for improving the surface quality of epitaxial wafers. At the same time, we also studied the influence of hydrogen etching on the quality of epitaxial wafers. The experimental results show that proper hydrogen etching can optimize surface quality, but excessive etching may lead to the exposure of substrate defects. Therefore, it is necessary to carefully control the conditions of hydrogen etching in practical applications to avoid adverse effects. These findings have important guiding significance for optimizing the quality of epitaxial wafers. Full article

In this study, a 4H-SiC homoepitaxial layer was grown on a 150 mm 4° off-axis substrate using a horizontal hot wall chemical vapor deposition reactor. Comparing C₃H₈ and C₂H₄ as C sources, the sample grown with C₂H₄ exhibited a slower growth rate and lower doping concentration, but superior uniformity and surface roughness compared to the C₃H₈-grown sample. Hence, C₂H₄ is deemed more suitable for commercial epitaxial wafer growth. Increasing growth pressure led to decreased growth rate, worsened thickness uniformity, reduced doping concentration, deteriorated uniformity, and initially improved and then worsened surface roughness. Optimal growth quality was observed at a lower growth pressure of 40 Torr. Furthermore, the impact of buffer layer growth on epitaxial quality varied significantly based on different C/Si ratios, emphasizing the importance of selecting the appropriate conditions for subsequent device manufacturing. Full article

The rough morphology at the growth surface results in the non-uniform distribution of indium composition, intentionally or unintentionally doped impurity, and thus impacts the performance of GaN-based optoelectronic and vertical power electronic devices. We observed the morphologies of unintentionally doped GaN homo-epitaxially grown via MOCVD and identified the relations between rough surfaces and the miscut angle and direction of the substrate. The growth kinetics under the effect of the Ehrlich–Schwoebel barrier were studied, and it was found that asymmetric step motions in samples with a large miscut angle or those grown at high temperature were the causes of step-bunching. Meandering steps were believed to be caused by surface free energy minimization for steps with wide terraces or deviating from the $[1\overline{1}00]$ m-direction. Full article

In this study, a 4H-SiC homoepitaxial layer was grown on a 150 mm 4° off-axis substrate using a horizontal hot-wall CVD reactor. The research aimed to investigate the impact of varying the C/Si ratio and temperature while also changing the N₂ flow rate and N₂ flow ratio on the growth rate (thickness), doping, surface roughness, and uniformity of the large-size 4H-SiC epitaxial layer. The results indicate that the growth rate and thickness uniformity of the film increases with an increase in the C/Si ratio. Additionally, adjusting the N₂ flow rate in a timely manner based on the change in the C/Si ratio is crucial to achieving the best epitaxial layer doping concentration and uniformity. The study found that, as the temperature increases, the film thickness and thickness uniformity also increase. The maximum thickness recorded was 6.2 μm, while the minimum thickness uniformity was 1.44% at 1570 °C. Additionally, the surface roughness reached its lowest point at 0.81 nm at 1570 °C. To compensate for the difference in thickness and doping concentration caused by temperature distribution and uneven airflow, the N₂ flow ratio was altered. In particular, at a growth temperature of 1570 °C, a N₂ flow ratio of 1.78 can improve the uniformity of doping by 4.12%. Full article

Conventional deep-ultraviolet (UV) light-emitting diodes (LEDs) based on AlGaN crystals have extremely low light-emission efficiencies due to the absorption in p-type GaN anode contacts. UV-light-transparent anode structures are considered as one of the solutions to increase a light output power. To this end, the present study focuses on developing a transparent AlGaN homoepitaxial tunnel junction (TJ) as the anode of a deep-UV LED. Deep-UV LEDs composed of n⁺/p⁺-type AlGaN TJs were fabricated under the growth condition that reduced the carrier compensation in the n⁺-type AlGaN layers. The developed deep-UV LED achieved an operating voltage of 10.8 V under a direct current (DC) operation of 63 A cm⁻², which is one of the lowest values among devices composed of AlGaN tunnel homojunctions. In addition, magnesium zinc oxide (MgZnO)/Al reflective electrodes were fabricated to enhance the output power of the AlGaN homoepitaxial TJ LED. The output power was increased to 57.3 mW under a 63 A cm⁻² DC operation, which was 1.7 times higher than that achieved using the conventional Ti/Al electrodes. The combination of the AlGaN-based TJ and MgZnO/Al reflective contact allows further improvement of the light output power. This study confirms that the AlGaN TJ is a promising UV-transmittance structure that can achieve a high light-extraction efficiency. Full article

This paper reviews some of the basic issues in homoepitaxial growth of III-nitrides to enable a vertical device technology. It focuses on the use of metal organic chemical vapor deposition (MOCVD) to grow GaN and explores the effects of the native substrate characteristics on material quality, interface composition, and device performance. A review of theoretical work understanding dopants in the ultra-wide III-nitride semiconductors, AlN and BN, is also included for future efforts expanding the technology into those materials. Full article

The quality of the N-doped 4H-SiC homoepitaxial layers grown via hot-wall horizontal chemical vapor deposition (CVD) was evaluated at various C/Si ratios (1.0–1.2) and growth temperatures (1570–1630 °C). The microstructure and morphology of the epilayers were studied through a comparative analysis of the AFM patterns under different growth conditions. X-ray photoelectron spectroscopy and Raman spectroscopy revealed the quality of the 4H-SiC epilayers and the amount of N-doping. It was found that an increase in the C/Si ratio enabled obtaining a quite smooth epitaxial layer surface. Moreover, only the 4H-SiC crystal type was distinguished in the epilayers. In addition, the epitaxial quality was gradually improved, and the amount of defect-related C-C bonds significantly dropped from 38.7% to 17.4% as the N doping content decreased from 35.3% to 28.0%. An increase in the growth temperature made the epitaxial layer surface smoother (the corresponding RMS value was ~0.186 nm). According to the Raman spectroscopy data, the 4H-SiC forbidden mode E₁(TO) in the epilayers was curbed at a higher C/Si ratio and growth temperature, obtaining a significant enhancement in epitaxial quality. At the same time, more N dopants were inserted into the epilayers with increasing temperature, which was opposite to increasing the C/Si ratio. This work definitively shows that the increase in the C/Si ratio and growth temperature can directly enhance the quality of the 4H-SiC epilayers and pave the way for their large-scale fabrication in high-power semiconductor devices. Full article

The homoepitaxial growth of 4H-SiC films was conducted on 4H-SiC 150 mm 4° off-axis substrates by using a home-made hot-wall chemical vapor deposition (CVD) reactor. Special attention was paid to the influence of the growth temperature on the surface morphology, growth rate, doping efficiency, and structural uniformity of the films. Among the above factors, growth temperature and flow ratio were shown to be the essential parameters to produce high-quality homoepitaxial layers. Furthermore, a two-side flow tunnel was introduced to control the growth temperature nonuniformity in the reactor. The influence of flow ratio on the epitaxial layer uniformity was also studied. It was found that the surface roughness increased with the increasing temperature, achieving its minimum value of 0.183 nm at 1610 °C. Besides that, the film growth rate decreased with the increase in growth temperature, whereas the degrees of thickness non-uniformity, N₂ doping non-uniformity, and doping efficiency increased. Meanwhile, both the thickness and doping uniformity can be improved by adjusting H₂ and N₂ flow ratios, respectively. In particular, the use of the H₂ ratio of 1.63 and N₂ ratio of 0.92 enabled one to increase the degree of uniformity of thickness and doping by 0.79% (standard deviation/mean value) and 3.56% (standard deviation/mean value), respectively, at the growth temperature of 1630 °C. Full article

The use of low-temperature (LT) GaAs layers as dislocation filters in GaAs/Si heterostructures (HSs) was investigated in this study. The effects of intermediate LT-GaAs layers and of the post-growth and cyclic in situ annealing on the structural properties of GaAs/LT-GaAs/GaAs/Si(001) HSs were studied. It was found that the introduction of LT-GaAs layers, in combination with post-growth cyclic annealing, reduced the threading dislocation density down to 5 × 10⁶ cm⁻², the root-mean-square roughness of the GaAs surface down to 1.1 nm, and the concentration of non-radiative recombination centers in the near-surface GaAs/Si regions down to the homoepitaxial GaAs level. Possible reasons for the improvement in the quality of near-surface GaAs layers are discussed. On the one hand, the presence of elastic deformations in the GaAs/LT-GaAs system led to dislocation line bending. On the other hand, gallium vacancies, formed in the LT-GaAs layers, diffused into the overlying GaAs layers and led to an increase in the dislocation glide rate. It was demonstrated that the GaAs/Si HSs obtained with these techniques are suitable for growing high-quality light-emitting HSs with self-assembled quantum dots. Full article