Low temperature (100 °C) atomic layer deposited-ZrO2 for recessed gate GaN HEMTs on Si

초록

In this paper, the effect of atomic layer deposited ZrO2 gate dielectrics, deposited at low temperature (100 degrees C), on the characteristics of recessed-gate High Electron Mobility Transistors (HEMTs) on Al0.25Ga0.75N/GaN/Si is investigated and compared with the characteristics of those with ZrO2 films deposited at typical atomic layer deposited (ALD) process temperatures (250 degrees C). Negligible hysteresis (Delta V-th < 20 mV), low gate leakage current (I-g@ 2V = 6.6 x 10(-6) A/cm(2)), high breakdown voltage (> 4 V), and low interfacial state density (D-it = 3.69 x 10(-11) eV(-1) cm(-2)) were observed on recessed gate HEMTs with similar to 5nm ALD-ZrO2 films grown at 100 degrees C. The excellent properties of recessed gate HEMTs are due to the absence of an interfacial layer and an amorphous phase of the film. An interfacial layer between 250 degrees C-ZrO2 and GaN is observed via high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. However, 100 degrees C-ZrO2 and GaN shows no significant interfacial layer formation. Moreover, while 100 degrees C-ZrO2 films maintain an amorphous phase on either substrate (GaN and Si), 250 degrees C-ZrO2 films exhibit a polycrystalline-phase when deposited on GaN and an amorphous phase when deposited on Si. Contrary to popular belief, the low-temperature ALD process for ZrO2 results in excellent HEMT performance. Published by AIP Publishing.

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