Time-/Current-Dependent Surge Current Capability of Fully-Vertical GaN-on-GaN PiN Diode With Conductivity Modulation

Bipolar-mode operation is essential for surge current ruggedness of diodes in high-power applications. Different from indirect-bandgap Si and SiC, it is unclear whether hole injection in the direct-bandgap GaN can yield effective conductivity modulation and consequently enhance surge current tolerance. In this article, we systematically investigate the evolvement of surge current capability in a fully-vertical GaN-on-GaN PiN diode with surge pulsewidth (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t} _{\text {surge}}$ </tex-math></inline-formula>) varying from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu $ </tex-math></inline-formula>s to 10 ms and peak surge current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {peak}}$ </tex-math></inline-formula>) up to 17.8 kA/cm2. Thanks to the desirable conductivity modulation even in the direct-bandgap GaN, the vertical GaN-on-GaN PiN diode exhibits a low differential specific <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-resistance of 0.45 m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot $ </tex-math></inline-formula>cm2 and a high surge energy density of 282 J/cm2 in a 10-ms surge current test. In conjunction with the microsecond-level dynamic I–V characterizations, the photon-enhanced and thermally-enhanced conductivity modulation in GaN has been identified and analyzed, which plays an important role in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${t} _{\text {surge}}$ </tex-math></inline-formula>-/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {peak}}$ </tex-math></inline-formula>-dependent surge current characteristics. The desirable photon-enhanced and thermally-enhanced conductivity modulation and superior surge current capability show the potential of vertical GaN bipolar devices in high-power electronic applications.