In Situ Dielectric Al₂O₃/β‐Ga₂O₃ Interfaces Grown Using Metal–Organic Chemical Vapor Deposition

Abstract

as the gate dielectric for device applications. For transistor applications, a gate dielectric should exhibit low leakage currents, have low interface trap densities to achieve a controllable threshold voltage (V T ), and should also have a higher breakdown field compared to the underlying semiconductor. Many insulators such as SiO 2 , [3][4][5][6] Al 2 O 3 , [7,8] SiN, [9] and HfO 2 [9,10] have been studied as a gate oxide material and passivation layers for gallium oxide devices. Extreme permittivity materials such as barium titanate (BaTiO 3 ) were also studied and used as dielectric material in β-Ga 2 O 3 -based transistors and heterojunction Schottky barrier diodes. [11][12][13] Complex oxides such as ternary rare earth alloys (Y 0.6 Sc 0.4 ) 2 O 3 were also investigated by Masten et al. as gate dielectric for β-Ga 2 O 3 -based metal oxide semiconductor (MOS) structures. [14] Among all the dielectric materials, Al 2 O 3 is studied and used most extensively for β-Ga 2 O 3 -based devices due to its compatibility with β-Ga 2 O 3 . Chabak et al. demonstrated various lateral MOSFETs with Al 2 O 3 as gate dielectric showing excellent field strength. [15][16][17] Li et al. also demonstrated β-Ga 2 O 3 -based vertical FinFET structures with outstanding figure of merit (FOM) using Al 2 O 3 as gate dielectric. [18][19][20] Jian et al. studied the effects of PDA on the interface trap density of the ALD deposited Al 2 O 3 on (001) β-Ga 2 O 3 . [21] In all these reported works the deposition of Al 2 O 3 is primarily performed using ex situ technique such as atomic layer deposition (ALD), where after its growth, the gallium oxide substrate or epilayer is taken to a different reactor for dielectric deposition. During such a transfer step, it is hard to completely remove any interface contamination. Using in situ deposition of Al 2 O 3 in the same reactor as the underlying Ga 2 O 3 , the surface of the Ga 2 O 3 can be kept pristine without exposure to the ambient. The quality of the dielectric could also improve due to the high temperature growth by metalorganic chemical vapor deposition (MOCVD) (500 to 1000 °C), compared to ALD (100 to 300 °C). MOCVD also enables high deposition rates, significantly higher than that of the ALD technique. MOCVD reactor can also facilitate high temperature in situ annealing which can reduce the dielectric/semiconductor interface state density as well as improve the bulk dielectric quality. The in situ growth of Al 2 O 3 on both Ga-face and N-face GaN has been studied extensively using MOCVD. [22][23][24][25][26] In this paper, we demonstrate for the first time in situ growth of Al 2 O 3 using MOCVD and High quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. This paper reports the in situ metal-organic chemical vapor deposition of Al 2 O 3 on β-Ga 2 O 3 as a potentially better alternative to the most commonly used atomic layer deposition (ALD). The growth of Al 2 O 3 is performed in the same reactor as Ga 2 O 3 using trimethylaluminum and O 2 a...

(Invited, Digital Presentation) Exploring the Potential and Limits of Gallium Oxide Electronics: In-Situ Dielectrics, Heterointegration and High-k Field Plates

“…To determine density of all the all the interface states and their energy dependence deep ultra-violet (DUV) assisted CV measurements were performed. The detailed description of the methodology is provided elsewhere (31). The MOSCAPs were first taken from D-A, and kept at accumulation for 10 minutes to fill all the traps.…”

“…Various reports exist on the study of dielectric on β-Ga 2 O 3 to improve the interface quality and breakdown field (24)(25)(26)(27)(28)(29)(30). In this paper we discuss the improvement of interface quality between the dielectric and β-Ga 2 O 3 using in-situ MOCVD-grown Al 2 O 3 , where Al 2 O 3 is grown on βGa 2 O 3 in the same reactor without breaking the vacuum (31). We also discuss the design of an optimum β-Ga 2 O 3 schottky barrier diode (SBD) (32) using p-type III-nitride guard rings for enhanced breakdown to circumvent the absence of p-type doping (33).…”

Measurement and gate-voltage dependence of channel and series resistances in lateral depletion-mode β-Ga2O3 MOSFETs

“…Improved growth, material quality and fabrication techniques lead to rapidly increasing β-Ga 2 O 3 power device performance with breakdown voltages, V BR , up to 8.32 kV, breakdown fields up to 6.45 MV cm −1 , and high power figure of merit up to 13.2 GW cm −2 [7][8][9][10][11][12][13][14][15][16][17]. Field-effect transistors (FETs) designed for radio frequency performance have also been fabricated [18][19][20].…”

Ultimate low leakage and EOT of high-κ dielectric using transferred metal electrode

“…To address this issue, one strategy to scaling Si CMOS technology under limited static power consumption is to employ materials with a high dielectric constant (high-κ) as the gate dielectric layer, which allows the EOT and supply voltage (V dd ) to be reduced at the single-transistor level. Most of the studies reported substituting SiO 2 with high-κ materials, such as HfO 2 [8][9][10], ZrO 2 [11][12][13], Al 2 O 3 [14][15][16] as a gate oxide. However, in current Si-based device development, high-κ materials have a lattice mismatch with Si, making high-κ materials difficult to grow on the surface of Si with good quality.…”