Schottky barrier height of Au on the transparent semiconducting oxide β-Ga2O3

Abstract

The Schottky barrier height of Au deposited on (100) surfaces of n-type β-Ga2O3 single crystals was determined by current-voltage characteristics and high-resolution photoemission spectroscopy resulting in a common effective value of 1.04 ± 0.08 eV. Furthermore, the electron affinity of β-Ga2O3 and the work function of Au were determined to be 4.00 ± 0.05 eV and 5.23 ± 0.05 eV, respectively, yielding a barrier height of 1.23 eV according to the Schottky-Mott rule. The reduction of the Schottky-Mott barrier to the effective value was ascribed to the image-force effect and the action of metal-induced gap states, whereas extrinsic influences could be avoided.

Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

“…When the temperature increases from 21 C to 150 C, eV bi is found to decrease from 1.12 eV to 0.9 eV, while eU B presents a very slight decrease only from 1.39 eV to 1.3 eV. Our experimental eU B values are comparatively large, in agreement with or larger than the other experimental and theoretical ones for the Pt/Ga 2 O 3 contacts, 21,23,36 and obviously larger than those in the Cu/ Ga 2 O 3 , 22 Au/Ga 2 O 3 , 24 and Ni/Ga 2 O 3 37 Schottky contacts. The reason for the weak temperature dependence of eU B is that E c À E f increases with temperature as seen from Eqs.…”

“…This current density is comparable to the reported highest values in the Pt/Ga 2 O 3 Schottky diodes, 21,23 and much larger than those in Cu/ Ga 2 O 3 , 22 and Au/Ga 2 O 3 diodes. 24 From the fitting line of the linear region in Figure 2(b), we can abstract that the threshold voltage or built-in potential (V bi ) is about 1.07 V. From the slope of the fitting line, the ON-resistance (R ON ) is about 159 X or 12.5 mX cm 2 , which is relatively high because of the low conductivity and carrier density of the substrate, but comparable to the reported values in the Pt/Ga 2 O 3 Schottky diodes. 21,23 In the inset of Figure 2(b), by linearly extrapolating J to zero voltage, the saturation current density (J 0 ) is determined to be 2 Â 10 À16 A/cm 2 , and from the subthreshold slope the ideality factor (n) can be got as about 1.1, which is close to unity.…”

“…The easy, low-cost, and mass-producible melt-growth methods at atmospheric pressure, such as floating zone (FZ) 17,18 and the edge-defined film-fed growth (EFG), [19][20][21] have been utilized to fabricate the single-crystal b-Ga 2 O 3 substrates. Schottky diode based on the b-Ga 2 O 3 (001), 21 ( 201), 20,22 and (010) 23 substrate has been studied, but (100)-oriented bulk single crystal is rarely used in SBD, 24 especially by the EFG method. At the same time, the b-Ga 2 O 3 (100) substrate can be obtained by mechanical exfoliation method and has the advantage of easy fabrication, low surface layer damage, and ultra-smooth crystal surface.…”

“…This value is also low enough compared to those of the previously reported Pt/Ga 2 O 3 , 21,23 Cu/ Ga 2 O 3 , 22 and Au/Ga 2 O 3 Schottky diodes. 24 According to the thermionic emission theory, we can abstract the other performance parameters of the diode. The thermionic emission current density (J) with a relationship to the applied voltage (V A ) is expressed as 22,29,30 …”

Perspective—Opportunities and Future Directions for Ga2O3

“…However, the lower thermal conductivity of Ga 2 O 3 relative to other wide bandgap materials means these techniques must be even more Contacts on n-Ga 2 O 3 .-The usual approaches involve surface etching or cleaning to reduce barrier height or increase of carrier concentration of the surface through preferential loss of oxygen. 10,12,[23][24][25] To date, contact schemes involving IZO or dry etching in BCl 3 /Ar to enhance the surface n-type conductivity, followed by Ti/Au annealed at 500…”