In this work, we have designed a novel gas inlet structure for efficient usage of growth and doping precursors. Our previous gas injection configuration is that the gas is mixed to one pipe first, then divided into two pipes, and finally entered the chamber symmetrically above the substrate without a jet nozzle. The distance between gas inlet and substrate is about 14.75 cm. Our new design is to add a new tube in the center of the susceptor, and the distance between the new tube and substrate is about 0.5 cm. In this new design, different gas injection configurations have been planned such that the gas flow in the reactor aids the transport of reaction species toward the sample surface, expecting the utilization efficiency of the precursors being improved in this method. Experiments have shown that a high doping efficiency and fast growth could be achieved concurrently in diamond growth when methane and diborane come from this new inlet, demonstrating a successful implementation of the design to a diamond microwave plasma chemical vapor deposition system. Compared to our previous gas injection configuration, the growth rate increases by 15-fold and the boron concentration increases by ~ 10 times. COMSOL simulation has shown that surface reaction and precursor supply both have a change in determining the growth rate and doping concentration. The current results could be further applied to other dopants for solving the low doping efficiency problems in ultra-wide-band-gap semiconductor materials.

High efficiency of boron doping and fast growth realized with a novel gas inlet structure in diamond microwave plasma chemical vapor deposition system
    Abstract
    1 Introduction
    2 Experimental
    3 Results and discussion
        3.1 Diamond growth without boron doping
        3.2 Diamond growth with boron doping
    4 Conclusions
    Acknowledgements 
    References

• Yan Teng(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Weikang Zhao(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Kun Tang(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Kai Yang(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Gengyou Zhao(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Shunming Zhu(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Jiandong Ye(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)
• Shulin Gu(College of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China)