Magneto-Transport Study of Undoped and Fe-doped AlGaN/GaN

The beating pattern of Shubnikov-de Haas oscillations for six samples of AlGaN/GaN heterostructures due to the spin-splitting of 2DEG have been observed. Two series of samples grown by metal-organic vapor phase epitaxy (MOVPE) were used in the study. One is undoped Al$_{x}$Ga$_{1-x}$N/GaN with different x values (x= 0.17, 0.29, 0.33), and the other is Fe-doped Al$_{x}$Ga$_{1-x}$N/GaN with the x values of 0.18, 0.19 and 0.21. The Shubnikov-de Haas measurements were performed at T = 0.3K for the magnetic field from 0.25 to 12 Tesla. The persistent photoconductivity (PPC) effect was used to vary the carrier concentration of the samples. The largest spin-splitting energy was observed on the sample of Fe-doped Al$_{0.21}$Ga$_{0.79}$N/GaN to be 5.96meV. After extended illuminated time, the carrier concentration of Fe-doped AlGaN/GaN increased at least 23{\%}; meanwhile the undoped AlGaN/GaN just produced 10.7{\%} increment at most. We found that the Fe-doped AlGaN/GaN exhibited higher PPC effect than the undoped samples.