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Gallium nitride (GaN) based transistors have been of interest to power electronics community because of their high breakdown voltage, high sheet carrier density, and the high saturation velocity of GaN. The low switching losses of GaN enable high-frequency operation which reduces bulky passive components with negligible change in efficiency [1,2]. The most established GaN electronic devices are fabricated on the Ga-polar orientation of GaN. Recently, N-polar GaN based devices are being explored for high frequency applications due to their advantages over Ga-face, such as lower contact resistance since the 2DEG is contacted through a lower bandgap material and better electron confinement due to natural back-barrier provided by the charge inducing barrier [3]. In this work, the first N-polar GaN current aperture vertical electron transistor is presented. The samples were grown by metal-organic chemical vapor deposition on c-plane Sapphire substrate. Mg ions were implanted at 80keV (dose: 1×〖10〗^15 〖cm〗^(-2)) into the top GaN layer, everywhere except the current aperture to form the current blocking layer. A 7 A^0 AlN to reduce alloy scattering followed by 150nm UID N-polar GaN as channel were regrown on top of the implanted structure. The 2DEG density and the mobility of the as-grown sample, determined using Hall measurement, were 1.1×〖10〗^13 〖cm〗^(-2) and 1800 〖cm〗^2/(V-S) , respectively. The CAVET showed excellent device modulation and a maximum current of 2 KA〖cm〗^(-2) at V_G=2V. The maximum transconductance per mm of source was 140 mS. The device had a very large pinch-off voltage of -14V as calculated due to the presence of high charge density in the channel.
[1] S. Chowdhury et al 2013 Semicond. Sci. Technol. 28 074014
[2] J. Millán, et al 2014 IEEE Transactions on Power Electronics, 29, 2155
[3] Uttam Singisettiet al 2013 IOP Semicond. Sci. Technol. 28 074006
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