Tianning Xu

Transparent Thin-Film Transistors Using ZnMgO as Dielectrics and Channel

An enhancement-mode ZnMgO transparent thin-film transistor (TFT) is fabricated, in which cubic-phase ZnMgO (C-ZnMgO) is used as gate insulator and hexagonal-phase ZnMgO (H-ZnMgO) is used as channel. The multilayers of C-ZnMgO and H-ZnMgO are grown on patterned indium-tin-oxide-coated glass in successive fashion at low temperature. Capacitor-voltage characteristics measured across the gate show that the H-ZnMgO channel is n-type. The C-ZnMgO isolating layer demonstrates low leakage current characteristics, i.e., 4 times 10-7 A/cm2, at a bias of 10 V. The transparent TFTs display a typical channel mobility of 1.5 cm2 V-1 s-1 and an on/off ratio of 104.

Refractive indices of cubic-phase MgxZn1-xO thin-film alloys

Refractive indices for cubic-phase MgxZn1−xO (0.55⩽x⩽1) thin-film alloys were determined from transmission measurements and Manifacier envelope method. The refractive index of cubic MgxZn1−xO decreases with the Mg fraction increase, such as at the wavelength of 400nm the refractive index decreases from 1.89 to 1.73 as x increases from 0.57 to 1.0. The refractive index dispersion relation of cubic MgxZn1−xO in the visible-light region (400–800nm) follows the first-order Sellmeier equation and decreases with the increase of Mg fraction.

Annealing effect on electrical properties of high-k MgZnO film on silicon

Cubic crystalline MgZnO was grown on p-type Si (0?0?1) by a reactive e-beam evaporation system at low temperature. AES depth profiles for the MgZnO films demonstrate good uniformity of Mg, Zn and O components. MIS capacitors were fabricated and C?V and I?V characterizations were performed to evaluate the annealing effect on electrical properties of MgZnO films. High temperature annealing up to 900 ?C under O2 ambient significantly improves C?V and I?V characteristics. The interface trapped charges decrease from 5.30 ? 1012 cm?2 to 2.48 ? 1011 cm?2 as the annealing temperature increases from 550 ?C to 900 ?C, indicating the quality improvement of the interfacial layer. Meanwhile the density of mobile charges increases from 1.93 ? 1010 cm?2 to 1.72 ? 1011 cm?2 as the annealing temperature increases from 550 ?C to 900 ?C, which is attributed to the evaporation of O near the surface and migration of Zn2+ towards the surface from MgZnO alloy film under such high temperatures.

Observation of thermal-misfit strain relaxation in a PbTe semiconductor grown on Cd0.96Zn0.04Te(1?1?1)

The thermal-misfit strain relaxation in epitaxial PbTe grown on Cd0.96Zn0.04Te(1 1 1) substrates has been studied by the combined characterization of atomic force microscopy and high-resolution transmission electron microscopy. It is shown that the strain relaxes by the movement of dislocations in the 1 1 0–{1 0 0} primary glide system and leaves straight slip steps on the surface. The thermal-misfit strain relaxation is greatly affected by the growth temperature and post-growth cooling rate. Post-growth treatment with a slower cooling rate improves the crystalline quality of PbTe grown on Cd0.96Zn0.04Te(1 1 1). Because of the easy dislocation glide down to the interface in the 1 1 0–{1 0 0} primary glide system, PbTe/Cd0.96Zn0.04Te(1 1 1) heterostructures exhibit good crystal and optical qualities, which indicate that PbTe/CdZnTe heterostructures may become a promising candidate for the fabrication of PbTe-based mid-infrared optoelectronic devices.