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 Ga ₂ O ₃ power devices. In this work, majority and minority carrier traps in beta-gallium oxide ( $\beta $ -Ga ₂ O ₃ ) have been investigated and identified by means of deep level transient spectroscopy (DLTS) in Ni/ $\beta $ -Ga ₂ O ₃ Schottky barrier diode (SBD) and NiO/ $\beta $ -Ga ₂ O ₃ p ⁺ -n heterojunction diode (HJD). For both diodes, a dominant energy level of majority carrier (electron) trap states is determined to be ${E}_{C}-$ (0.75–0.79) eV with a concentration of (2.4–4.1) $\times 10^{{13}}$ cm $^{-{3}}$ . Meanwhile, an additional trapping level at ${E}_{V} +0.14$ eV with a concentration of 1.2 $\times 10^{{14}}$ cm $^{-{3}}$ yield is present in NiO/ $\beta $ -Ga ₂ O ₃ bipolar HJD but absent in the Ni/ $\beta $ -Ga ₂ O ₃ SBD unipolar counterpart. The detection of such minority carrier traps originates from the hole injection through trap-assisted tunneling (TAT) from $\text{p}^{+}$ -NiO to $\beta $ -Ga ₂ O ₃ . The bias- and frequency-dependent DLTS characteristics identify that such shallow-level minority carrier traps are located in the $\beta $ -Ga ₂ O ₃ bulk region rather not interfacial states at the NiO/ $\beta $ -Ga ₂ O ₃ 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 Ga ₂ O ₃ -based unipolar and bipolar power devices.