Plasma-etch-free <i>β</i>-Ga2O3–NiO–PtO<i>x</i> merged PiN Schottky diode with high-voltage stress reliability

A gallium oxide (Ga2O3)–nickel oxide (NiO) merged PiN Schottky (MPS) diode was fabricated using Ga flux plasma-free etch and platinum oxide (PtOx) contacts. The use of a plasma-etch-free process enables the fabrication of Ga2O3 trenches with low surface damage. PtOx acts as both a Schottky contact to n-type Ga2O3 and an Ohmic contact to p-type NiO. Compared to the Ni/NiO contact used in many prior devices, the PtOx/NiO contact exhibits a 100 times lower contact resistance as shown by linear transfer length method measurements. This improved contact resistance boosts the diode’s forward current capacity, as featured by a second turn-on in the current–voltage characteristics with a decreased differential on-resistance. This verifies the concurrent current conduction through both Schottky and PN junctions and thereby the formation of a MPS diode. Furthermore, MPS diodes were subjected to high reverse bias reliability testing. Such a reliability test has been seldom reported in Ga2O3 devices. During an 800 V stress test (80% of the breakdown voltage) for a cumulative time of 2000 s, MPS diodes were periodically switched on, showing no degradation in the dynamic on-state characteristics. This signifies a stable PtOx–Ga2O3 Schottky contact and an improved Ga2O3–NiO heterojunction with minimal sidewall trapping as a result of the plasma-etch-free process.