In this work, a detailed numerical simulation is carried out to model the current–voltage characteristics of a nickel/β-Ga2O3 Schottky barrier diode at different temperatures. These SBDs are produced using confined magnetic-field-based sputtering to deposit the nickel (Ni) Schottky contact of the diode. This method reduces the thickness of the defect area created by plasma and argon bombardment, and consequently, the electrical characteristics are less affected by temperature changes or annealing (i.e. the device is more stable). During annealing, Ni diffuses into β-Ga2O3. A model for this diffusion is proposed in this work, in which Ni diffusion reduces the defects produced by plasma and argon bombardment by filling the Ga vacancy. Furthermore, Ni diffusion produces a new interfacial compound, namely (N i x G a 1 − x ) 2 O 3 at the interface between the Ni and the β-Ga2O3. This new compound layer has different properties than those of β-Ga2O3, in particular, those of the bandgap and the affinity. Finally, the temperature-dependent current-density–voltage (J–V) characteristics are simulated, taking the proposed model into account. A good agreement with measured values is achieved, especially at low forward voltages, which demonstrates the soundness of the proposed model.

In this work, the temperature-dependent parameters of Ni/β-Ga2O3 Schottky barrier diode (SBD) were analyzed and modeled. The simulation is to elucidate the physical phenomenon behind this temperature dependence. At room temperature, the deviation of SBD parameters from the ideal case is due to the Schottky barrier height ( ϕ B ) inhomogeneity. A model is developed for this inhomogeneity in which an interfacial defected layer (IDL) is formed. Defects (extrinsic states) are related to plasma and Ar atom bombardment used in the confined magnetic field-based sputtering to realize the Ni Schottky contact diffusion in β-Ga2O3. Ni diffuses, upon annealing, to compensate defects in this IDL. It was found that the Schottky barrier height ( ϕ B ) and threshold voltage V Th decrease with increasing temperature. This decrease is related to intrinsic and extrinsic states (plasma and Ar bombardment). However, the ideality factor (η) increases which is related to the series resistance (R S) increase. The increase is related to the interfacial layer and nickel resistance increase with increasing temperature.

The reverse leakage current under high reverse voltage of a Ni/β-Ga 2 O 3 Schottky barrier diode (SBD) is numerically modelled and compared to measurements. universal Schottky tunnelling, thermionic emission and image-force lowering were taken into account. Furthermore, when type conversion under high reverse voltage has occurred at the top interface between Ni and β-Ga 2 O 3 and the SBD behaved as P–i–N diode, band to band tunnelling is proposed in association with the usually used Selberherr’s Impact ionization to model avalanche breakdown. The obtained breakdown voltage and specific on-resistance value are 434 V and 2.13 mΩ·cm2, respectively, fairly close to measurement values of 440 V and 2.79 mΩ·cm2. Optimization is performed based on the insertion of an intrinsic layer between Ni and the β-Ga 2 O 3 drift layer. It was found that 0.4 μm gave better Baliga’s figure of merit of 9.48107 W·cm−2 with breakdown voltage and specific on-resistance of 465 V and 2.28 mΩ·cm2, respectively. Finally, a surface edge termination design based on TiO2 insulator plate is adopted and the best obtained breakdown voltage, Baliga’s figure of merit and specific on-resistance were 1466 V, 1.98 × 109 W·cm−2 and 1.98 mΩ·cm2 respectively.

Schottky barrier diodes (SBD) are usually qualified by their figures of merit. Evolution of these figures of merit with temperature is an indication of the different conduction mechanisms involved in SBD. Figures of merit extraction at different temperatures is therefore of great importance. Thermionic emission conduction modeling of I–V characteristics is usually considered when extracting these figures of merit. However, high-ideality factor values are obtained at low temperatures because of other conduction mechanisms involved. In this work, TCAD simulation is used to model measured Ni/β-Ga2 O3 SBDs at a temperature range of 100–300 K. This modeling separates tunneling current from thermionic emission current; hence, a reasonable ideality factor of 6.04 was obtained from the total current. An ideality factor of about 1.04 was extracted from the thermionic current component only. Evolution with temperature of this combination of tunneling and thermionic emission is examined. It is concluded that, with increasing temperature, tunneling is reduced while thermionic emission is increased; thus, an ideality factor is almost independent of temperature and close to unity is obtained.

No abstract

No abstract

No abstract

Controlling the Schottky barrier height (ϕB) and other parameters of Schottky barrier diodes (SBD) is critical for many applications. In this work, the effect of inserting a graphene interfacial monolayer between a Ni Schottky metal and a β-Ga2O3 semiconductor was investigated using numerical simulation. We confirmed that the simulation-based on Ni workfunction, interfacial trap concentration, and surface electron affinity was well-matched with the actual device characterization. Insertion of the graphene layer achieved a remarkable decrease in the barrier height (ϕB), from 1.32 to 0.43 eV, and in the series resistance (RS), from 60.3 to 2.90 mΩ.cm2. However, the saturation current (JS) increased from 1.26×10−11  to 8.3×10−7(A/cm2). The effects of a graphene bandgap and workfunction were studied. With an increase in the graphene workfunction and bandgap, the Schottky barrier height and series resistance increased and the saturation current decreased. This behavior was related to the tunneling rate variations in the graphene layer. Therefore, control of Schottky barrier diode output parameters was achieved by monitoring the tunneling rate in the graphene layer (through the control of the bandgap) and by controlling the Schottky barrier height according to the Schottky–Mott role (through the control of the workfunction). Furthermore, a zero-bandgap and low-workfunction graphene layer behaves as an ohmic contact, which is in agreement with published results.