Impurity Compensation Effect Induced by Tin Valence Change in α-Ga1.4Sn0.6O3 Thin Films

Corundum-structured α-phase Ga1.4Sn0.6O3 thin films have been deposited on m-plane Al2O3(300) substrates using laser molecular beam epitaxy technology. With increasing of the oxygen partial pressure, the crystal lattice of Ga1.4Sn0.6O3 films expands due to tin ions valence changes from Sn4+ to Sn2+. The resistivity of the film deposited under 3 × 10–5 Pa is 3.54 × 104 Ω·cm, which decreases by about 2 orders of magnitude than that fabricated under 3 × 10–1 Pa. The mixture valence of Sn2+ and Sn4+ ions leads to the impurity altitude compensation effect. The deep ultraviolet photodetector based on α-phase Ga1.4Sn0.6O3 thin films was fabricated. With the oxygen partial pressure reducing gradually, the dark current and the photocurrent increase, and the relaxation time constants diminish, respectively.