β- Ga2O3 Schottky barrier height improvement using Ar/O2 plasma and HF surface treatments

Schottky barrier height (SBH) enhancement directly translates into increased breakdown voltage (VBR) of β-Ga2O3 Schottky barrier diodes (SBDs). In this work, ultra-thin (5, 10, and 15 Å) oxygen-rich AlOx interfacial layers (ILs), deposited using plasma-enhanced atomic layer deposition, are shown to enhance the SBH of post-metallization oxygen annealed Pt/AlOx/β-Ga2O3 SBDs by up to 0.8 eV resulting in a maximum VBR of nearly 500 V (2× gain) on 2–4 × 1016 cm−3 doped substrates, without compromising the specific on-resistance. The SBH and VBR enhancement is observed on (2¯ 01) as well as (001) surfaces. X-ray photoelectron spectroscopy (XPS) analysis shows that excess oxygen interstitial concentration in 5 Å AlOx films decreases (increases) with increasing thickness (oxygen anneal), making them more stoichiometric. The decreasing (increasing) trend in SBH and VBR with increasing IL thickness (oxygen anneal) is consistent with the XPS-derived O/Al ratio of the films and the formation of an AlOx/β-Ga2O3 interfacial dipole due to a difference in oxygen areal densities. The AlOx deposition can be easily integrated with field management methods such as field plates and guard rings that can further enhance β-Ga2O3 SBD performance.

Barrier height enhancement in β-Ga2O3 Schottky diodes using an oxygen-rich ultra-thin AlOx interfacial layer

Prajapati,

Lodha

2024

Monolithic β-Ga2O3 bidirectional dual-gate MOSFET

Sharma,

Chakrabarty,

Prajapati

et al. 2024

We report a monolithic bidirectional dual-gate metal–oxide–semiconductor field-effect transistor fabricated on epitaxially grown β-Ga2O3, demonstrating efficient two-way conduction and blocking. It features two independently controlled gates and operates in four distinct modes, offering flexibility in managing current and voltage in the first and third quadrants. This versatility makes it ideal for various power conversion system applications. The device operates at a low negative threshold voltage (∼−2.4 V for both gates), with a zero turn-on drain voltage and an on-resistance of approximately 500 Ω· mm. It exhibits a high on/off current ratio of 107 in all three conducting modes. In the blocking mode, the device breakdown was measured to be higher than ± 400 V. The estimated breakdown field and power figure of merit for the device are 0.4 MV/cm and 2.1 MW/cm2, respectively.

Electric field management in β-Ga2O3 vertical Schottky diodes using high-k bismuth zinc niobium oxide

Sharma,

Parasubotu,

Lodha

2024

In this work, we have integrated bismuth zinc niobium oxide (BZN), a high-k dielectric material, in metal–insulator–semiconductor (MIS) and field-plated metal–semiconductor (FP-MS) Schottky barrier diodes on β-Ga2O3. This increases the breakdown voltage (VBR) from 300 to 600 V by redistributing the electric fields, leveraging the high permittivity of BZN (k ∼ 210). Enhancement in Schottky barrier height, by approximately 0.14 eV for MIS and 0.28 eV for FP-MS devices, also contributes to the improved VBR. BZN inclusion has minimal impact on specific on-resistance (Ron,sp). Additionally, the devices display excellent current–voltage characteristics with ideality factors close to unity and an on/off current ratio greater than 1010. This work presents the most significant VBR enhancement reported-to-date for MIS devices on β-Ga2O3 without compromising turn-on voltage and Ron,sp. A comparison of FP-MS and MIS devices shows that FP-MS outperforms MIS in terms of lower Ron,sp, higher Schottky barrier height, and improved VBR.