Majority and Minority Carrier Traps in NiO/β-Ga2O3 p+-n Heterojunction Diode

Identifying defects/traps is of vital importance for the implementation of high-performance Ga₂O₃ power devices. In this work, majority and minority carrier traps in beta-gallium oxide (<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃) have been investigated and identified by means of deep level transient spectroscopy (DLTS) in Ni/<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ Schottky barrier diode (SBD) and NiO/<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ p⁺-n heterojunction diode (HJD). For both diodes, a dominant energy level of majority carrier (electron) trap states is determined to be <inline-formula> <tex-math notation="LaTeX">${E}_{C}-$ </tex-math></inline-formula>(0.75–0.79) eV with a concentration of (2.4–4.1) <inline-formula> <tex-math notation="LaTeX">$\times 10^{{13}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{-{3}}$ </tex-math></inline-formula>. Meanwhile, an additional trapping level at <inline-formula> <tex-math notation="LaTeX">${E}_{V} +0.14$ </tex-math></inline-formula> eV with a concentration of 1.2 <inline-formula> <tex-math notation="LaTeX">$\times 10^{{14}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{-{3}}$ </tex-math></inline-formula> yield is present in NiO/<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ bipolar HJD but absent in the Ni/<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ SBD unipolar counterpart. The detection of such minority carrier traps originates from the hole injection through trap-assisted tunneling (TAT) from <inline-formula> <tex-math notation="LaTeX">$\text{p}^{+}$ </tex-math></inline-formula>-NiO to <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃. The bias- and frequency-dependent DLTS characteristics identify that such shallow-level minority carrier traps are located in the <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ bulk region rather not interfacial states at the NiO/<inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ heterointerface. The identification of both majority and minority carrier traps in this work may shed light on the in-depth understanding of carrier transport mechanisms in Ga₂O₃-based unipolar and bipolar power devices.