Annealing temperature dependence of band alignment of NiO/β-Ga₂O₃

Abstract

The band alignment of sputtered NiO on β-Ga2O3 was measured by x-ray photoelectron spectroscopy for post-deposition annealing temperatures up to 600 °C. The band alignment is type II, staggered gap in all cases, with the magnitude of the conduction and valence band offsets increasing monotonically with annealing temperature. For the as-deposited heterojunction, ΔE V = −0.9 eV and ΔE C = 0.2 eV, while after 600 °C annealing the corresponding values are ΔE V = −3.0 eV and ΔE C = 2.12 eV. The bandgap of the NiO was reduced from 3.90 eV as-deposited to 3.72 eV after 600 °C annealing, which accounts for most of the absolute change in ΔE V−ΔE C. Differences in thermal budget may be at least partially responsible for the large spread in band offsets reported in the literature for this heterojunction. Other reasons could include interfacial disorder and contamination. Differential charging, which could shift peaks by different amounts and could potentially be a large source of error, was not observed in our samples.

Temperature Dependence of Low‐Frequency Noise Characteristics of NiOx/β‐Ga2O3 p–n Heterojunction Diodes

“…In our estimate, the change in bandgap for the NiO x layer between 300 and 400 K is less than 0.1 eV (E g (300 K) = 3.84 eV and E g (400 K) = 3.76 eV). [52] A recent study has shown that rapid thermal annealing of NiO x /𝛽-Ga 2 O 3 heterojunction diodes can provide significant improvement in the quality of the p-n diode interface, accompanied by a decrease in the interfacial defect states acting as recombination centers. [53] In the reported study, annealing was performed at 225 °C in an N 2 atmosphere to improve Ga 2 O 3 /NiO interface quality.…”

“…In our estimate, the change in bandgap for the NiO x layer between 300 and 400 K is less than 0.1 eV ( E g (300 K) = 3.84 eV and E g (400 K) = 3.76 eV). [ 52 ]…”

Superior high temperature performance of 8 kV NiO/Ga2O3vertical heterojunction rectifiers

“…[14][15][16][17] Both types can conduct 4100 A cm À2 at 4 V. Note that the R ON in the heterojunction rectifiers does not continue to decrease at forward voltages beyond B3 V. It has also been shown that the band alignment remains type II, staggered gap with the magnitude of the conduction and valence band offsets increasing monotonically with annealing temperature. 12 Fig. 3 shows the reverse J-V characteristics for both types of devices at different temperatures.…”

“…1,3,4 To achieve a high-power figure of merit, a rectifier must have a low drift layer concentration, with high electron mobility, as well as low R ON , and optimized edge termination to prevent current crowding. 1,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The breakdown voltage is larger for thicker drift layers, but this degrades the on-resistance. In addition, vertical geometry devices are desirable, because of their higher power conversion efficiency and absolute currents compared to lateral devices.…”

“…The lack of a practical p-type doping capability for Ga 2 O 3 has led to integration with p-type oxides to form p-n heterojunctions with the n-type Ga 2 O 3 . [9][10][11][12][13][14][15][16] The most successful of these has been NiO, generally deposited by sputtering. The forward current transport mechanism in such junctions is typically recombination at low biases and trap-assisted tunneling at higher bias.…”