• Mahapatra, Rajat
• Mitrovic, Ivona Z.
• Thayne, Iain G.
• Jones, Leanne
• Das, Partha
• Manzanera, Teresa Partida
• Potter, Richard J.
• Roberts, Joseph
• Dhanak, Vinod R.
• Gibbon, James
• Chalker, Paul R.
• Cho, Sung-Jin

Abstract

GaN high electron mobility transistors (HEMTs) have been commercially available for over 10 years, however gate leakage limits their performance. The HEMT has the advantages of offering simple associated circuit design and fail-safe operation. Currently the GaN based Metal-Insulator-Semiconductor (MIS)-HEMT device is seen to demonstrate superior performance in power electronics applications over the Schottky gate counterpart, due to its inherently lower gate leakage current, together with the ability to provide larger forward gate voltage swing by engineering the threshold voltage between depletion and enhancement mode operation and also an improved gate-drain breakdown voltage. High band gap gate dielectric materials are preferable as they can provide higher tunnelling barriers for electrons and holes, which result in lower gate leakage current. On the other hand, high dielectric constant (high-k) material is also necessary for improved electrostatic control over the channel and improved on-current, which in-turn results in higher transconductance. The quality of the gate dielectric and the dielectric/GaN interface plays a central role in device performance due to potential problems arising from fixed oxide charge, border and interface traps. The leakage current issue has been mitigated using Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, SiO<jats:sub>2</jats:sub> and Si<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub>, but comes at a cost of device transconductance degradation and undesirable threshold voltage shifts. A number of high-k dielectrics such as HfO<jats:sub>2</jats:sub>, ZrO<jats:sub>2</jats:sub>, Ta<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub>, LaLuO<jats:sub>3</jats:sub> and TiO<jats:sub>2</jats:sub> have been investigated to resolve this issue.</jats:p>

Topics

• impedance spectroscopy
• mobility
• dielectric constant
• semiconductor