Incomplete Ionization of a 110 meV Unintentional Donor in β-Ga₂O₃ and its Effect on Power Devices

Understanding the origin of unintentional doping in Ga₂O₃ is key to increasing breakdown voltages of Ga₂O₃ based power devices. Therefore, transport and capacitance spectroscopy studies have been performed to better understand the origin of unintentional doping in Ga₂O₃. Previously unobserved unintentional donors in commercially available [Formula: see text] Ga₂O₃ substrates have been electrically characterized via temperature dependent Hall effect measurements up to 1000 K and found to have a donor energy of 110 meV. The existence of the unintentional donor is confirmed by temperature dependent admittance spectroscopy, with an activation energy of 131 meV determined via that technique, in agreement with Hall effect measurements. With the concentration of this donor determined to be in the mid to high 10¹⁶ cm^-3 range, elimination of this donor from the drift layer of Ga₂O₃ power electronics devices will be key to pushing the limits of device performance. Indeed, analytical assessment of the specific on-resistance (R_onsp) and breakdown voltage of Schottky diodes containing the 110 meV donor indicates that incomplete ionization increases R_onsp and decreases breakdown voltage as compared to Ga₂O₃ Schottky diodes containing only the shallow donor. The reduced performance due to incomplete ionization occurs in addition to the usual tradeoff between R_onsp and breakdown voltage.