Toward Determination of the Critical Breakdown Field in Rutile Sn 1‐ x Ge x O 2 Alloys

The high‐field electronic transport characteristics of ultra‐wide bandgap (UWBG) rutile Sn 1‐ x Ge x O 2 alloys have been investigated through high‐voltage measurements using lateral metal–semiconductor–metal (MSM) structures. Undoped Sn 1‐ x Ge x O 2 thin films with a Ge composition of x ≈ 0.70 were epitaxially grown on c‐plane sapphire substrates via pulsed‐laser deposition at 650°C. MSM structures were fabricated using Pt contacts with contact spacings ranging from 0.5 to 2.7 μm to probe the voltage‐dependent transport behavior under high electric fields. The best devices demonstrated the ability to sustain applied voltages approaching 900 V prior to breakdown. Electrostatic simulations were used to evaluate the electric field distribution in the channel for the varying gap spacings and showed that the electric field in the channel is roughly three‐fourths of the applied voltage divided by the contact spacing, leading to an estimate of the critical breakdown field in the range of 7.0 ± 1.4 MV/cm. These results are encouraging that UWBG Sn 1‐ x Ge x O 2 alloys could have potential for applications in high‐power electronics.