Deep level acceptors of Zn-Mg divalent ions dopants in β-Ga2O3 for the difficulty to p-type conductivity

β-Ga2O3 exhibits huge potential applications in next-generation power electronics with its wide band gap, large breakdown field and high Baligas's figure of merit. The achievement of p-type conductive β-Ga2O3 faces hugely challenge due to the self-compensating process, while that is critically important to further extend its utility and applications. Although the acceptor deep levels of divalent ions dopants can explain the difficulty of p-type Ga2O3 theoretically, while the experimental evidence is lacked. Herein, Zn and Zn-Mg co-doped β-Ga2O3 thin films were prepared to investigate the acceptor levels of ZnGa and MgGa. The XPS results indicate that both Zn and Mg exhibit divalent ions when they replaced trivalent Ga ion. The doping concentration and band gap can modulate by solely changing the numbers of Zn and Mg pieces during the deposition process. The levels of ZnGa and MgGa are located at 0.79 eV and 1.00 eV respectively speculated by photoluminescence, such deep acceptor transition levels proved that it is difficult to obtain highly conductive p-type Ga2O3 by doping with divalent ions of Zn and Mg.