Zhaoqing Feng

Temperature dependent electrical properties of pulse laser deposited Au/Ni/β-(AlGa)2O3 Schottky diode

We have demonstrated the epitaxial growth of a β-(Al0.08Ga0.92)2O3 film on a β-Ga2O3 (010) substrate through pulsed laser deposition. The temperature-dependent electrical characteristics of Au/Ni/β-(Al0.08Ga0.92)2O3 Schottky diodes were investigated in the temperature range of 300–573u2009K, using thermionic emission theory to calculate the Schottky diode parameters. The barrier height ϕb was found to increase, while the ideality factor n and the series resistance Rs were found to decrease with increasing temperatures. The calculated values of ϕb and n varied from 0.81u2009eV and 2.29 at 300u2009K to 1.02u2009eV and 1.65 at 573u2009K. The temperature-dependent I-V characteristics of the Schottky diode have shown the Gaussian distribution, yielding a mean barrier height of 1.23u2009eV and a standard deviation of 0.147u2009V, respectively. A modified Richardson plot of ln(Is/T2)−(q2σs2/2k2T2) versus q/2kT gives ϕb0¯ and A* as 1.24u2009eV and 44.3 A cm−2u2009K−2, showing the promise of Ni/β-(AlGa)2O3 as a Schottky diode rectifier.

Influence of annealing atmosphere on the performance of a β-Ga 2 O 3 thin film and photodetector

β-Ga2O3 epitaxial thin films were deposited by laser molecular beam epitaxy (LMBE) and annealed at 800°C for 30 minutes in air and oxygen atmospheres, respectively. Photodetectors were fabricated using as-grown and annealed Ga2O3 epilayers. The influence of the annealing atmosphere on the crystal structure and optical properties of Ga2O3 films was investigated. X-ray diffraction (XRD) measurements show that the in-plane compressive strain of Ga2O3 thin films could be relaxed after high temperature thermal annealing. Compared with the as-grown sample, the annealed samples exhibit a red shift of absorption edge in the transmittance spectra, indicating a reduced bandgap. According to the XPS measurement results, the atomic ratios of O to Ga also increased for the annealed samples. Moreover, the oxygen-annealed photodetector achieves a larger photocurrent, higher responsivity and better time-dependent photoresponse than the other two samples, which may be attributed to the decrease in the number of oxygen vacancies.

Tin-assisted growth of ε-Ga 2 O 3 film and the fabrication of photodetectors on sapphire substrate by PLD

The growth of single crystal e-Ga2O3 films under the assistance of Sn element was studied using pulsed laser deposition (PLD). The crystal structure, optical properties and chemical state of the element were investigated to analyze the influence of tin during the film epitaxy. There is a transition layer at the substrate and the e-Ga2O3 film interface. Increase in Sn atomic ratio will cause a rise in the transition layer thickness and the growth rate. In addition, due to the Sn atoms aggregation and the formation of clusters, the higher dark current (Idark), photocurrent (Iphoto) and responsivity (R) were achieved for the enhanced electron transportation in the e-Ga2O3 metal-semiconductor-metal (MSM) photodetectors. The optical bandgap Eg determined from R increased from 4.81eV to 4.88eV and 4.94eV with Sn contents increasing from 0.9% to 1.2% and 1.5%, consistent with the transmittance results.