MOVPE-Grown β-Ga₂O₃ Lateral Power Transistors with V_BR Exceeding 4 kV

In this work, we report on the demonstration of &gt; 4.5kV breakdown in β-Ga₂O₃ lateral MESFETs using MOVPE-grown β-Ga₂O₃ channel and regrown contact layers. We demonstrate the use of gate-pad-connected field plate (GPFP) design in a β-Ga₂O₃lateral MESFET using a silicon nitride (SiN_x) dielectric deposited using PECVD. This work highlights that high breakdown voltages (kVs) and high lateral figure of merit (LFOM) can be achieved simultaneously in β-Ga₂O₃ lateral transistors.<br/>Growth of β-Ga₂O₃ channel (230 nm thick Si-doped ~3.6×10¹⁷cm^-3) on a Fe-doped (010) bulk substrates was performed using Agnitron Technology’s Agilis 700 MOVPE reactor with TEGa, O₂ and silane (SiH₄) as precursors and argon as carrier gas. The source/drain ohmic contacts were selectively regrown using a SiO₂ mask patterned using a low power SF₆/Ar ICP dry etching and wet etching [1]. The Si-doping in the regrown n+ layer was ~ 2.6×10²⁰cm^-3_.The total R_C in the device measured was 1.6 ± 0.2 Ω.mm [2]. The gate field plate metal was deposited after the deposition of SiN_x (170 nm thick) passivation layer. The gate field plate metal was electrically connected to the gate pad (shorted) outside the device mesa. The active region was finally passivated using a SiN_x/SiO₂ (50nm/50 nm) bilayer dielectric deposition using PECVD.<br/>The output and transfer curves of the β-Ga₂O₃ MESFET with an L_GD = 35μm were measured. The devices exhibited a max ON current (I_DMAX) of 56 mA/mm and a high I_ON/I_OFF ratio &gt; 10⁸. Three terminal breakdown measurements were performed at V_GS = -20V in a Fluorinert solution. The devices show very low reverse leakage until catastrophic breakdown occurs. The highest measurable V_BR recorded was 4565V (L_GD=45μm). From TCAD simulations, it was estimated that devices with L_GD &gt;10 μm had non-punchthrough (NPT) field profile at breakdown. These NPT devices (L_GD &gt;10 μm) show large dispersion in V_BR compared to the PT devices (L_GD ≤10 μm). This observation can be attributed to process variation over the 10 ×15 mm² sample. Nevertheless, I_DMAX for devices up to 45 μm L_GD show very small dependence on process variation.<br/>The achieved V_BR values and V_BR-R_on,sptrade-off is compared with the existing state-of-the-art literature reports on other device technologies such as GaN HEMTs, SiC, Diamond, and β-Ga₂O₃lateral devices. Our devices show some of the highest E_AVG (= V_BR/L_GD) and V_BR values simultaneously. The highest LFOM recorded was 132 MW/cm² for a V_BR of ~ 4.4kV. Our devices exhibit the lowest R_onsp values reported for any β-Ga₂O₃lateral device with V_BR &gt; 4kV to date. Our demonstration shows the potential of β-Ga₂O₃ FETs for future power device applications in the medium-voltage range.