Effects of surface passivation films on AlGaN/GaN HEMT with MIS gate structure

Abstract

We investigated the effect of ebeam‐deposited SiNx, SiO2, and TiO2 passivation films on the AlGaN/GaN HEMT structure. The AlGaN/GaN heterojunction structure was grown on a sapphire substrate by metal organic chemical vapor deposition. The sheet resistance of the AlGaN/GaN HEMT structure was 420‐510 Ω/□. TiO2, SiNx and SiO2 passivation films were employed as the insulator in MIS gate structure. All passivation films were deposited by electron beam evaporation at 200 °C. The thickness of SiNx, SiO2 and TiO2 passivation films were 15, 10 and 15 nm, respectively. The relative dielectric constants of the deposited SiNx, SiO2 and TiO2 were measured to be 4, 7 and 80, respectively by fabricating the capacitance structures. The sheet resistance was changed after the deposition of the insulator films. We found to be 512, 628 and 992 Ω/□ for the SiNx, SiO2 and TiO2 films, respectively. We considered that the surface passivation using the TiO2 and SiO2 films reduces the carrier density in the AlGaN/GaN channel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterization of AlGaN/GaN MISHFETs on a Si substrate by static and high-frequency measurements

“…Moreover, the AlGaN/GaN/SiC MISHFETs show higher microwave output power than the HFET counterparts [3]. Various insulators have been used to investigate the properties of AlGaN/GaN MISHFETs on sapphire ( [4,5] and references therein) and SiC substrates ( [6,7] and references therein). However, less is reported on AlGaN/GaN MISHFETs on Si substrates according to our knowledge.…”

Investigations of AlGaN/GaN MOS-HEMT with Al2O3deposition by ultrasonic spray pyrolysis method

“…In addition, the deposited oxide layer can also serve as surface passivation to relieve the problems of Fermi level pinning under the gate electrode and to reduce RF current collapse [4,5]. A variety of oxide materials have been applied to the MOS-gate structure such as Si 3 N 4 [6,7], SiO 2 [8,9], HfO 2 [10][11][12], ZrO 2 [11,12], La 2 O 3 [13,14], TiO 2 [15], Er 2 O 3 [16], and Al 2 O 3 [17][18][19][20][21][22][23]. Among them, Al 2 O 3 has advantages of high relative permittivity (k ∼ 10), good thermal stability (amorphous up to 1000 °C), high breakdown field (>5 MV cm −1 ), and wide band-gap (9 eV).…”