Solidification and Crystal Growth Laboratory



    This research project will focus on the understanding of melt growth characteristics of germanium-silicon (Ge-Si) alloy crystals, which are promising candidates in thermopower generation, photovoltaics, cell phones, handsets, GPS systems, collision warning systems, and data converters.

    Melt growth allows large-scale production of semiconductor crystals. However, growth of Ge-Si single crystals from melt is extremely sensitive to experimental parameters. Obtaining accurate thermal data near the solid/liquid (s/l) interface and so knowing the fluid flow characteristics during Ge-Si alloy crystals are essential to control the growth, which is not easy with conventional techniques. Especially, because of widely varying segregation coefficient, large density differences, and large solidification range in the case of Ge-Si growth, it is important to keep the interface planar at a constant temperature to avoid compositional fluctuations that may lead to interface instability and degradation of single crystallinity.

    An innovative approach (Axial Heat Processing -AHP-) will be used in this study. The AHP technique will permit close control of convective effects and thermal field near the growth interface. AHP achieves these by using a heater immersed in melt near s/l interface. Power and position of the heater can be controlled as desired to promote planar interface and laminar fluid flow. Such parameters as the fluid flow, concentration fields in the melt and solid, and interface shape, position, and temperature will be assessed. All these growth parameters then will be correlated to interface stability, namely the transition from single to cellular or dendritic growth.

    As Ge-Si alloys find use in microelectronics in different industries, high quality Ge-Si alloy single crystals can especially serve Turkey’s space program as they can be used in applications to convert waste exhaust heat and solar power to useful energy that is needed in deep space exploration vehicles as well as in applications on earth such as those mentioned in the opening paragraph. This research may also initiate new industrial fields in Turkey, hence resulting in new employment opportunities.











Assoc.Prof. E.Balikci