Analysis of the Formation of the Off-State Leakage Current in p-GaN HEMT

In this study, the off-state leakage current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {off}}$ </tex-math></inline-formula>) of p-GaN high electron mobility transistor (HEMT) is analyzed. At low drain bias approximately below 100 V, the leakage is dominated by the punchthrough leakage current from the source electrode, resulting in an increase in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {off}}$ </tex-math></inline-formula> as the bias increases. However, at an intermediate drain bias to 400 V, the punchthrough leakage current will decrease because of the gate electron injection. The electrons will be injected into the GaN buffer layer, indirectly leading to a decrease in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {off}}$ </tex-math></inline-formula>. Lastly, at a higher drain bias of 700 V, the dominant leakage path is converted into the body current, which is dominated by the trap-assisted thermionic field emission (TA-TFE) mechanism. The generated holes will recombine with the injected electrons or inject into the buffer layer, leading to a significant increase in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {off}}$ </tex-math></inline-formula>. The reliability testing is also employed to validate the underlying mechanisms.