【Member Papers】Proposal and Simulation of β-Ga₂O₃ Hetero-Junction Schottky Diodes With Low Work-Function Anode and High Breakdown Voltage

      Researchers from the Xidian University have published a dissertation titled "Proposal and Simulation of β-Ga₂O₃ Hetero- Junction Schottky Diodes With Low Work-Function Anode and High Breakdown Voltage" in IEEE Journal of the Electron Devices Society.

Background

      β-Ga₂O₃ is an attractive semiconductor material for high power and high frequency electronic applications due to its unique material properties, such as high critical electric field (E_c) of ~8 MV/cm from its ultra-wide bandgap of 4.5-4.9 eV, decent intrinsic electron mobility of ~200 cm²V^-1 s^-1 as well as a high electron saturation velocity of ∼2×10⁷ cm/s, which gives Ga₂O₃ a theoretical Baliga’s figure-of-merit (BFOM) and Johnson’s figure-of-merit (JFOM) to be several times higher than that of SiC and GaN. In addition to these superior material properties, β-Ga₂O₃ is advantageous when it comes to material growth methodologies. β-Ga₂O₃ bulk single crystal can be grown by melt-grown methods, which allows for the production of low-cost, large-size, and high-quality commercial compatible substrates. This also enables high-quality homoepitaxy and reveals the enormous potential of β-Ga₂O₃ for future wide spread high-power applications.

Abstract

      In this work, we propose a p-NiO/n-Ga₂O₃ hetero-junction (HJ) Schottky barrier diode (SBD) with low turn-on voltage (V_on) and high breakdown voltage (BV) with a trench SBD as a control. An investigation of its electrical characteristics is simulated by Sentaurus TCAD. The HJ SBD utilizes a low work-function anode metal to form a top electrode by reducing the V_on of the diode at the forward state. A fin structure and metal/semiconductor (M/S) junction or PN HJ was employed to achieve an enhanced BV at the reverse state. An attempt to optimize the electrical characteristics of the device by modifying its structural parameters is also comprehensively analyzed in this work. The HJ SBD achieves a low V_on of 0.57 V and a Power Figure of Merit (P-FOM) of 3.79 GW/cm², simultaneously. The proposed structure provides a new approach for realizing high performance β-Ga₂O₃ SBDs with high reverse blocking and low loss capabilities.

Conclusion

      In summary, p-NiO/n-Ga₂O₃ HJ SBD structures with low V_on and high BV were proposed and investigated by Sentaurus TCAD simulations. This work has systematically studied the effect of the device V_on reduction strategies without significantly sacrificing the BV. This is done by changing the work-function of top anode and using Schottky contacts or HJs with fin structure to assist the fin side-wall depletion. Through the optimization of device parameters, a typical V_on of 0.57 V and P-FOM of 3.79 GW/cm² was simulated for the HJ SBD with an R_HW of 0.12, W_Fin of 5 μ m, W_Space of 3 μm, a T_NiO of 300 nm, and a top metal SBH of 0.9 eV. References indicate that Schottky contacts formed with metals like Ti and Mo in conjunction with β-Ga₂O₃ exhibit a Schottky Barrier Height close to our projected value. Additionally, future advancements in surface treatment could potentially reduce the SBH of the M/S contact, aligning it with our anticipated targets. Consequently, it is believed that the structure outlined in this article is capable of achieving the dual objectives of low V_on and high BV for future high power and low loss applications.