Materials Science Forum Vols. 615-617

Abstract: We investigated the effects of the solution growth process on the polytype and crystal quality of the crystals grown on (111) 3C-SiC seed crystals. In spite of the use of 3C-SiC seed crystals, the polytype of the grown crystal changed from 3C-SiC to 6H-SiC, because the stacking errors easily occur due to the similarity of the (111) face of 3C-SiC and the (0001) face of 6H-SiC. Moreover, the grown 6H-SiC crystal affected the crystal quality of the seed crystal, i.e., high-density stacking faults were induced in the seed crystal after the growth process.

Abstract: The conditions to succeed in growing 3C-SiC single crystals are first, make available large 3C-SiC seeds and second, develop a suitable growth process. In this paper, we will address those two issues by reviewing the most recent results in the field. Nucleation, growth, structural quality and doping results will be presented. New insights on 3C bulk growth will be discussed with respect to a future development of real bulk 3C-SiC ingots.

Abstract: Solution growth was performed using a free-standing (001) 3C-SiC epilayer as a seed crystal at a growth temperature of 1700°C. The seed crystal was prepared by a CVD method on the undulated Si substrate. 3C-SiC stably grew on the (001) seed crystal. However, dark stripes from the seed crystal to the grown crystal along {111} planes were clearly observed. The stripes were due to the high-density stacking faults extended from the stacking faults in the 3C-SiC epilayer that were induced during the CVD growth on Si substrate.

Abstract: The main problem for the development of 3C-SiC electronics is the lack of an adapted bulk growth process. The seeded sublimation method is not very adapted for the 3C polytype because of the solid-state transition from cubic to hexagonal that occurs at high temperature (above 1800°C). In this paper, we propose a new experimental set-up for the development of a solution route for the growth of high quality 3C-SiC crystals. By a coupled approach involving experiments and global process modeling, we have addressed the problems of dissolution and crystallization, elimination of parasitic nucleation and stabilization of the growth front. With an appropriate control of the different convection mechanisms, a stable growth front is demonstrated, with a growth rate of a few tens of µm/h at 1650°C. Further improvements and potentialities of this approach are discussed.

Abstract: We present a structural and optical investigation of nitrogen-doped single crystals of cubic silicon carbide prepared by the continuous feed - physical vapour transport method. Self-nucleated crystals were produced which exhibited well faceted square and triangular shapes. KOH etching was used to characterize the structural defects, like stacking faults and dislocations. The effect of changing the nitrogen flow rate on the different crystalline orientations was investigated by Raman spectroscopy and low temperature photoluminescence techniques.

Abstract: We report on recent advances in liquid phase epitaxial (LPE) conversion of a bulk Si wafer into self standing 3C-SiC. This includes the role of the stress control within the (100) oriented “crucibles”, the elaboration of crack-free (111) “crucibles” and the successful conversion of (100) and (111) oriented Si wafer. To date up to 100µm thick 3C-SiC(100) as well as 30µm thick crack-free 3C-SiC (111) materials have been obtained. The growth rate ranges from 20 to 100µm/h and locally can even reach ~1mm/h. In this work we focus on the structural, morphological and optical properties of the LPE-grown material.

Abstract: The growth rate of 4H-SiC epi layers has been increased up to 100 µm/h by chlorine addition. The epitaxial layers grown with this process have been characterized by electrical, optical and structural characterization methods. Very thick (> 100 µm) epitaxial layer has been grown and the Schottky diodes realized on these layers have good yield (> 87%) with a low defect density (10/cm2). This process gives the opportunity to realize very high power devices with breakdown voltages in the range of 10 kV or X-Ray and particle detectors with a low cost epitaxy process.

Abstract: Conversion of basal plane dislocations (BPD) to threading edge dislocations (TED) in 8° off-cut 4H-SiC within an n+ buffer layer would eliminate the nucleation site for Shockley-type stacking faults in active device regions grown on such buffer layers. To that end, the propagation and conversion of BPDs through in situ growth interrupts is monitored using ultraviolet photoluminescence (UVPL) wafer mapping. The optimized growth interrupt scheme lasts for 45 minutes with a propane mass flow of 10 sccm at growth temperature. This scheme has shown a conversion efficiency of up to 99% for samples with electron (hole) concentrations < 5x1014 cm-3 (8x1015 cm-3). Samples subjected to a 45 or 90 minute interrupt under 10 sccm of propane, regardless of conversion efficiency, exhibit a “slit” in the surface morphology associated with each BPD and oriented perpendicular to the off-cut and BPD propagation direction. Repetition of the optimal interrupt sequence with a 5 μm epilayer spacer grown between the two interrupts resulted in the same conversion efficiency as a single optimal growth interrupt. Incorporation of the optimal interrupt into an n+ layer is more complicated as attempts to do so in layers doped with nitrogen to 2x1018, 2x1017 and 2x1016 cm-3 resulted in conversion efficiencies of ~6%.

Abstract: The transfer and generation of extended defects in 4H-SiC epitaxial growth at a high growth rate are examined. An epilayer with virtually no basal plane dislocations (BPDs) is obtained using 4º off Si-face substrates, although the formation of 3C-polytype inclusions is occasionally observed. The behavior of BPDs and threading screw dislocations (TSDs) in epitaxial growth is also investigated by X-ray topography and transmission electron microscopy, and the propagation of BPDs and conversion and generation of TSDs in the epilayers are discussed.

Abstract: Using joined super-lattice Kinetic Monte Carlo simulations, continuous modelling and recent experimental data on the homoepitaxial growth of 4H Silicon Carbide we study the transition between monocrystalline and polycrystalline growth in terms of misorientation cut, growth rate and temperature. We compare these optimally calibrated results both with previous continuous models and literature data. We demonstrate that this study was, indeed, necessary to correctly reformulate the phase diagram of the transition.