The bulk growth process of SiC using the physical vapor transport (PVT) method may be called mature. The single crystalline diameter of 150 mm is state of the art, while the crystal diameter of 200 mm is strongly pushed to take over the pole position. Major R&D efforts focus on the further reduction of the dislocation density. In this context the improvement of the yield of the PVT process is a key task. This work discusses three aspects of the PVT growth process to reach a higher SiC crystal yield: (i) Type of the carbon isolation material and procedure to maintain process-to-process reproducible growth conditions. (ii) Pro and cons between temperature and power control (or mixture of both) of the SiC crystal growth phase of the PVT process, (iii) selection of a set of process parameters and specs of the grown SiC crystal which are a fingerprint of reproducible growth conditions (related to selection and design of hot zone isolation components). Note: Other sources for process instabilities like graphite quality of the carbon crucible, SiC seed quality and seed mounting (to name a few among many other distortive sources) are not addressed in this work. In our study we are analyzing 34 PVT 150 mm growth process, all making use of the fundamentally equal hot-zone design (index I) where two minor design variations (cooling channel, crucible variant) are included. Compared to an industrial standard growth process, the number of crystals compared are rather low. Nevertheless, the study resulted in clear recommendations how to increase the process reproducibility and yield related to the challenging isolation components of the hotzone. The 150 mm PVT growth runs were carried out in a Sicma 3 system provided by the company PVA Crystal Growing Systems GmbH (Wettenberg, Germany). The experimental study was supported by a precise computer simulation of the temperature field of hot zone which makes use of an advanced data base on high temperature (T<2000°C) heat conductivity of the applied carbon isolations. Carbon isolation: At process temperatures above 2000°C mainly carbon isolations are applied which withstand the growth conditions. Nevertheless, at such high temperatures, degradation because of microscopic morphologic changes and aging related to Si-containing leakage of vapor from the growth cell are very common. We have designed the hotzone in a way that about 25% of the carbon isolation is replaced by new material before each growth run. Using this procedure, the T-measurement by optical pyrometers on top of the growth cell indicated a high process reproducibility. In the case of an induction heating power of 15.5 kW, we observed a constant temperature of 2020°C which varied only by +/-20°C (see Table 1). This value variation is less than 1% which comes close to measurement precision of optical ratio pyrometers. In addition, the observed crystal growth rate (determined in the center of the boule) varied less than 3%. Both values indicate, that the evolution of the SiC crystal has become very reproducible. Power versus temperature process control: Considering a T-measurement error of optical pyrometers of at least +/-10°C at T>2000°C and potential distortions in the optical alignment of the system during the growth process, a total T-measurement error of 10-20°C is typical, Nevertheless, distortions above 50°C may occasionally occur. In addition, a thermally highly isolated hot-zone (to save heating energy) exhibits long reaction intervals before a change in the heating paper affects the hot-zone temperature. Therefore, it is recommended to use the temperature measurement/control as an indicator that the right T-value for a given heating power has been reached at the beginning of the growth process. Throughout the growth process a constant heating power mode (including a precise monitoring of the temperature of the hotzone) is recommended for stable growth process conditions. In fact, experimentally (for several different hot-zone designs & fixed inert-gas pressure) we observed an almost linear growth rate to temperature (or heating power) relation. Since the growth rate is dependent on many thermodynamic as well as growth-kinetic phenomena, this finding represents more like a rule of practice, which proved to be valuable for the planning of new PVT growth processes. Fig. 2 depicts the temperature to growth rate evolution for two 150 mm hot-zone designs (= different cooling channel dimensions). This result on one hand it indicated that the constant power process control may lead to stead (= undisturbed) growth process. On the other hand it enabled quite precise tuning of the SiC crystal growth rate. Indicators for reproducible growth conditions: The simple dataset of Heating power, Temperature of the hot-zone (top or bottom pyrometer) and the Growth rate (or crystal length at given duration of the growth period, see Fig. 1) as used in Table 1 proved to be powerful to validate reproducible growth condition which are related to the selection and design of hot zone isolation components as discussed in this work. The presentation will include a more detailed discussion of the dataset of the 34 growth process carried out for this study. In addition to the experimental data, we will use computer simulation results to point out to which extend certain in-homogeneities or batch-to-batch variations of the carbon isolations affect the crystal growth yield. This work has been partially funded by the German Science Foundation (contracts WE2107-12, WE 2107-15) and PVA Crystal Growing Systems GmbH (Wettenberg, Germany)(contract wtt-19174).