AlN/GaN HEMT with Gate Insulation and Current Collapse Suppression Using Thermal ALD ZrO2

Abstract

In this letter, we report the device characteristics of AlN/GaN MIS-HEMT on silicon substrate using thermal atomic-layer-deposition (ALD) ZrO2 with various thicknesses. The thermal ALD ZrO2 thin film is deposited at 250°C, which avoids plasma enhancement during the fabrication process. From the transmission electron microscopy results, it is found that the alloy penetrates to the 2DEG region to form a carrier conductive pathway which facilitates the ohmic contact formation. The optimized 7 nm-thick ZrO2 AlN/GaN MIS-HEMT exhibits improved Ion/Ioff ratio and suppressed current collapse degradation, compared with 4 nm-thick ZrO2 AlN/GaN MIS-HEMT and Schottky gate AlN/GaN HEMT (SG-HEMT). In addition, as compared to SG-HEMT, reverse gate leakage current can be reduced by about six orders and forward gate bias extends to + 6.3 V with 7 nm-thick ZrO2 AlN/GaN MIS-HEMT.