Yi-Jing Lin

High color purity phosphors of LaAlGe2O7 doped with Tm3+ and Er3+

Phosphors of LaAlGe2O7 doped with Tm3+ and Er3+ of high color purity, exhibiting a narrow band emission in the blue and green regions, were obtained. (La1−xLnx)AlGe2O7 (Ln=Tm,Er) powders are bright emitters, with chromaticity color coordinates that are comparable to or better than those of standard phosphors for display or lighting devices. The blue emission of the Tm3+-doped phosphor had CIE chromaticity coordinates (0.151, 0.033) with a dominant wavelength of 455nm and a color purity of 94%. The Er3+-doped phosphor had color coordinates (0.249, 0.718), a dominant wavelength of 542nm, and 92% purity.

Green-emitting phosphor of LaAlGe2O7:Tb3+under Near-UV irradiation

As the Tb 3+ -doped LaAlGe 2 O 7 phosphors were synthesized by solid-state method, their characterization and luminescent properties were also investigated. The extraordinary excitation spectra showed only intense f-f transition of Tb 3+ ions around near-UV region, while the 4f-5d transition could be neglected. Under excitation, the as-obtained powders emitted bright green light at 544 nm ( 5 D 4 → 7 F 5 ). By analyzing the decay curves, the energy migration between Tb 3+ ions is conspicuous in 5 D 3 → 7 F 5 transition due to the cross-relaxation in LaAlGe 2 O 7 . One of the interesting results of this work is that the excitation spectrum of the phosphor and the emission spectrum of the near-UV light-emitting diode (LED) have closely overlapped, which provides the potential as a near-UV LED converted phosphor in solid state lighting technology.

In0.34Al0.66As0.85Sb0.15/δ(n+)-InP heterostructure field-effect transistors

A lattice-matched δ-doped In0.34Al0.66As0.85Sb0.15/InP heterostructure field-effect transistor (HFET) which provides large band gap (∼1.8 eV), high Schottky barrier height (φB>0.73 eV), and large conduction-band discontinuity (ΔEc>0.7 eV) has been proposed. In0.34Al0.66As0.85Sb0.15/InP heterostructures are shown to be type II heterojunctions with the staggered band lineup. This HFET demonstrates a output conductance of less than 1 mS/mm. Two-terminal gate-source breakdown voltage is more than 20 V with a leakage current as low as 170 μA at room temperature. High three-terminal off-state breakdown voltage as high as 36 V, and three-terminal on-state breakdown voltage as high as 18.6 V are achieved. The gate voltage swing is also significantly improved.

High breakdown voltage symmetric double δ-doped In0.49Ga0.51P/In0.25Ga0.75As/GaAs high electron mobility transistor

A double δ-doped In0.49Ga0.51P/In0.25Ga0.75As/GaAs high electron mobility transistor has been successfully fabricated by metalorganic chemical-vapor deposition. Improved electron mobility as high as 5410 (19 200) cm2/V s at 300 (77) K along with turn-on voltage as high as 2.3 V and reverse gate-to-drain voltage up to 75 V are achieved. These characteristics are attributed to the use of the δ-doped, undoped InGaP Schottky layer, and undoped GaAs setback layer. Moreover, the parasitic parallel conduction can be eliminated. The activation energy is also deduced.

Low-leakage current and high-breakdown voltage GaAs-based heterostructure field-effect transistor with In0.5(Al0.66Ga0.34)0.5P Schottky layer

An In0.5(Al0.66Ga0.34)0.5P/GaAs heterostructure field-effect transistor has been fabricated by metal-organic chemical vapor deposition. A turn-on voltage as high as 3.2 V along with an extremely low gate reverse leakage current of 69 μA/mm at VGD=−40 V are achieved. In addition, it is found that the device can be operated with gate voltage up to 1.5 V without significant drain current compression. These characteristics are attributed to the use of high Schottky barrier height, high band gap of In0.5(Al0.66Ga0.34)0.5P Schottky layer, and to the large conduction-band discontinuity at the In0.5(Al0.66Ga0.34)0.5P/GaAs heterojunction.