Interface engineering of β-Ga2O3 MOS-type Schottky barrier diode using an ultrathin HfO2 interlayer

Low leakage current and high breakdown voltage are critically important to design high performance Schottky barrier diodes. In this work, a low leakage current was reported by studying the effect of inserting an ultrathin HfO2 layer using atomic-layer deposition with different cycle number at the interface between Ni and β-Ga2O3 for different annealing temperatures. A remarkable decrease in leakage current from 5.68 × 10−3 to 2.97 × 10−6 A/cm² at -300 V and a breakdown voltage increase from -467 to -556 V, were achieved when two cycles of HfO2 are inserted and annealed at 400°C. The leakage current decreases from 9.87 × 10−5 to 2.14 × 10−5 A/cm² for 200°C annealing temperature and from 1.035 × 10−4 to 2.56 × 10−6 A/cm² for as-deposited Metal-oxide semiconductor based Schottky barrier diode (MOSSBD) only after 2-cycles (∼2 Å) HfO2 is inserted. As the number of HfO2 cycles was increased (2–8 cycles) and the annealing temperature is varied, leakage current and breakdown voltage are affected. To investigate these variations in leakage current and breakdown voltage, Silvaco TCAD simulator is used. Good agreement is obtained between experiment and simulation by considering the fixed charge density in HfO2 (positive fixed charge density is related to oxygen vacancy density in HfO2 and the interfacial trap (reduced by annealing), and, where necessary, also considering the inhomogeneity of the Schottky barrier height to understand the main reason for the abrupt increase in leakage current at a specific reverse voltage.