Electrical Properties of Liquid Phase Deposited SiO[sub 2] on Photochemical Treated GaN

Abstract

The electrical characteristics of liquid phase deposited SiO 2 on GaN substrate were investigated. More Ga-OH bonds can be formed on GaN surface treated by KOH solution under a mercury arc lamp excitation. The OH bonds will absorb siloxane oligomer and enhance liquid phase deposited SiO 2 . A better quality of SiO 2 /GaN interface can be obtained and the interface state density is 1.24 ϫ 10 12 cm −2 eV −1 at the energy of 0.42 eV below the edge of conduction band. The leakage current density of the metal oxide semiconductor diode can be improved from 6.98 ϫ 10 −5 to 3.28 ϫ 10 −6 A/cm 2 at +1 MV/cm. GaN-based materials have been applied for the fabrication of optoelectronic devices such as light-emitting diodes, laser diodes, and photodiodes. They are also attractive for electronic devices due to their high electron saturation velocity and high breakdown voltage. Many efforts were devoted to insulators-GaN to fulfill the applications. For optoelectronic devices, SiO 2 is applied to different kinds of structures to realize light extraction like reflector, epitaxial lateral overgrowth, etc. 1,2 For electronic devices, SiO 2 passivation can suppress the drain current dispersion on GaN/AlGaN high electron mobility transistor ͑HEMT͒ due to the elimination of deep traps. 3,4 GaN metal oxide semiconductor field effect transistor ͑MOSFET͒ with SiO 2 as the gate oxide will result in lower gate leakage current especially for low noise and reliable power electronics compared with that of metal semiconductor field effect transistor ͑MESFET͒ with a Schottky gate. 5,6 Recently, SiO 2 deposition on GaN-based MOSFET as gate oxides was reported by different growth methods including plasma enhanced chemical vapor deposition ͑PECVD͒, 7 photochemical vapor deposition, 8 remote plasmaassisted oxidation, 9 Si diffused layer, 10 etc. However, the high leakage current densities of these MOS structures, mainly from the interface state density ͑D it ͒, need further improvement. The high D it is from the difficult binding between GaN and SiO 2 , and could be associated with the chemical stability of GaN.Liquid phase deposition ͑LPD͒ method has several advantages such as low deposition temperature ͑40°C͒, atmospheric growth, selective growth, good step coverage, and low cost. High quality LPD SiO 2 with very low leakage current density ͑ϳ10 −9 at A/cm 2 at 10 MV/cm͒ was prepared with the aqueous solutions of hydrofluosilicic acid ͑H 2 SiF 6 ͒ and boric acid ͑H 3 BO 3 ͒ 11 and has been applied in integrated circuit ͑IC͒ fabrication processes. 12,13 The chemical reactions for LPD SiO 2 have been proposed as follows 14,15 The silicon halide ͓SiF m ͑OH͒ 4−m ͔ can be hydrolyzed and changed into siloxane oligomer OH-͑SiO x ͒-OH by catalytic reactions. In Eq. 2, H 3 BO 3 is used as fluorine scavenger to drive Eq. 1 toward the right to promote SiO 2 deposition. The dehydration between siloxane oligomer and Si-OH existing on Si substrate surface forms SiO 2 film. 16,17 Therefore, the OH bond on substrate surface is essential for SiO 2 deposition. The...

Effects of N2O Postdeposition Annealing on Metal-Organic Decomposed CeO2 Gate Oxide Spin-Coated on GaN Substrate

“…1,2,9 A relatively low dielectric constant (k) SiO 2 has been used as a thick gate oxide in GaN-based MOS devices. [10][11][12][13] However, a high electric field is induced in the SiO 2 due to the low-k of SiO 2 (k ¼ 3.9) compared to GaN (k ¼ 9) and high critical electric field for GaN. This will cause reliability issues except that the SiO 2 gate oxide is substituted by a high-k gate oxide.…”

Improvement in Electrical Characteristics of Low-Pressure Chemical-Vapor-Deposited SiNxDielectric Layer on GaN Substrate by Ammonium Sulfide Treatment

“…2 shown in the inset indicates that Frenkel-Poole emission is the main mechanism causing the leakage current. The leakage current density is much lower than those of other GaN MOS structures with oxides prepared with liquid-phase-deposited SiO 2 , 14) atomic-layer-deposited Al 2 O 3 , 15) and electron-beam-evaporated TiO 2 16) as dielectrics. This indicates that LPCVD is a good method for preparing low-leakage SiN x film on GaN.…”

Retardation Mechanism of Ultrathin Al2O3 Interlayer on Y2O3 Passivated Gallium Nitride Surface

“…Keeping in track with the development of gallium nitride (GaN)-based metal-oxide-semiconductor (MOS) devices for high power and high temperature applications, which strive to solve the ever-increasing demand of global energy consumption, challenges pertaining to the implementation of a high quality passivation layer on GaN substrate surface are inexorable. − Numerous low-dielectric constant ( k ) and high- k materials, which include SiO 2 , , SiN x O y , Al 2 O 3 , ,,, HfO 2 , , Sc 2 O 3 , Ga 2 O 3 (Gd 2 O 3 ), Gd 2 O 3 , Y 2 O 3 , , Ga 2 O 3 , , MgTiO 3 , Ta 2 O 5 , MgO, MgScO, CeO 2 , , and HfAlO, have been researched. Of these materials, the attention devoted to the utilization of Y 2 O 3 as the passivation layer in GaN-based MOS devices remains meager.…”