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...
This study investigates the growth of silicon oxide film on gallium nitride using hydrosilicofluoric acid and silica gel by the temperature‐difference liquid‐phase deposition. In the conventional liquid phase deposition, the boric acid is used as fluorine scavenger to prompt silicon oxide deposition and it also acts as an impurity in the oxide film. The better metal–oxide–semiconductor diode electrical characteristics can be obtained by the temperature‐difference method with lower boric acid incorporation and higher deposition rate. Compared with the leakage current density of the conventional and temperature‐difference methods, it can be much improved from 9.93 × 10–2 A/cm2 to 5.8 × 10–4 A/cm2 at +2 MV/cm and from 1.35 × 10–2 A/cm2 to 5.15 × 10–4 A/cm2 at –1 MV/cm. The effective oxide charges is improved from 3.88 × 1011 cm–2 to 2.27 × 1011 cm–2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The characteristics of a SiO2 film grown on (NH4)2Sx treated GaN by temperature‐difference liquid phase deposition were investigated. Hydrofluorosilicic acid and boric acid were used as deposition solutions. For GaN without the (NH4)2Sx treatment, an Al/SiO2/GaN MOS diode shows poor electrical characteristics due to the native oxides existing at the interface. With (NH4)2Sx treatment of GaN, a stable sulfide‐terminated surface is obtained and the leakage current density of SiO2/GaN is improved from 6.15 × 10–4 A/cm2 to 2.08 × 10–5 A/cm2 at the electric field of 2 MV/cm. The effective oxide charges decrease from 6.09 × 1011 C/cm2 to 2.23 × 1011 C/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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