AlGaN/GaN MISHEMTs on silicon using atomic layer deposited ZrO2 as gate dielectrics

Conventional Schottky-metal gate based GaN HEMTs (SB-HEMTs) suffer undesirable high gate leakage current (I
gleak
) issue. To reduce the I
gleak
, varieties of gate insulators like Si
3
N
4
, SiO
2
, Al
2
O
3
, Ga
2
O
3
, HfO
2
, Sc
2
O
3
etc. have been demonstrated to obtain high quality metal-insulator-semiconductor (MIS) structure. ZrO
2
, with a high dielectric constant (18–25 [1]) and large bandgap (5.2–7.8 eV [2]), is a good candidate for gate insulation layer. Compared with ZrO
2
prepared by other techniques, atomic layer deposited (ALD) technique has the benefits of nanometer scalability, high uniformity, good coverage, low defect density, etc. S. Abermann et al. [3] and A. Alexewicz et al. [4] have reported InAlN/GaN MISHEMTs using ALD ZrO
2
. However to-date, comprehensive study was not carried out in AlGaN/GaN MISHEMTs on Si with ALD ZrO
2
as insulator layer. In this paper, we demonstrated AlGaN/GaN MISHEMTs with ALD ZrO
2
as the gate dielectric layer on Si substrate. The use of ALD ZrO
2
dielectrics can effectively suppress the reverse gate leakage current and improve gate voltage up to +5 V.