Aluminum nitride (AlN) thin films were deposited by nitrogen-ion-assisted pulsed laser ablation of an AlN target. A KrF excimer laser with a pulse duration of 23 ns and a wavelength of 248 nm was used as a light source for the ablation. A nitrogen ion beam with energies in a range of 200–800 eV is used to assist the deposition. The nitrogen ion implantation can compensate the possible loss of nitrogen species in the ablated plasma and can effectively assist the deposition by providing energetic nitrogen ions. Raman and Fourier transform infrared spectroscopy measurements were used to characterize the deposited thin films. The influences of the substrate temperature and the ion energy on the electronic and structural properties of the deposited thin films were studied.
The energy-band structure and non-ultraviolet photoelectric properties of a Ni/n-Si/N + -SiC isotype heterostructure Schottky photodiode are simulated by using Silvaco-Atlas. There are energy offsets in the conduction and valance band of the heterojunction, which are about 0.09 eV and 1.79 eV, respectively. The non-UV photodiode with this structure is fabricated on a 6H-SiC(0001) substrate. 𝐽-𝑉 measurements indicate that the device has good rectifying behavior with a rectification ratio up to 200 at 5 V, and the turn-on voltage is about 0.7 V. Under non-ultraviolet illumination of 0.6 W/cm 2 , the device demonstrates a significant photoelectric response with a photocurrent density of 2.9 mA/cm 2 and an open-circuit voltage of 63.0 mV. Non-ultraviolet operation of the SiC-based photoelectric device is initially realized.
AlN films with a preferred orientation <002> have been prepared on Si(100) substrates via DC reactive magnetron sputtering. X-ray diffraction, atomic force microscopy, scanning electron microscopy, ellipsometer, and ultraviolet-visible-near infrared (UV-VIS-NIR) spectrophotometer were used to investigate the structural and optical properties of the AlN thin films. When the sputtering pressure is about 0.4 Pa, the flow ratio between nitrogen and argon is 1 : 3, and the growth temperature is 400°C, the transmissivity of the AlN film is about 90% in the visible and near-infrared region, and its optical band gap is~5.84 eV. The refractive index of the thin films is about 2.05, which is lower than the bulk AlN refractive index.
A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission, and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated. Special pretreatment and passivation for the chip facets were performed to achieve improved reliability performance. The laser chips were p-side-down mounted on the AlN sub-mount, and then tested at continuous wave (CW) operation with the heat-sink temperature setting to 25 °C using a thermoelectric cooler (TEC). As high as 60.5% of the wall-plug efficiency (WPE) was achieved at the injection current of 11 A. The maximum output power of 30.1 W was obtained at 29.5 A when the TEC temperature was set to 12 °C. Accelerated life-time test showed that the laser diodes had lifetimes of over 62 111 h operating at rated power of 10 W.
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