LEDs ♦ news digest
caused for example by changes in the power supply frequency. This ensures that the display backlighting remains constant.
No crosstalk with the proximity sensor
Crosstalk – an effect in which the emitted infrared light is reflected by the smartphone casing directly onto the receiver – is eliminated by the SFH 7776 in the component itself. Designers no longer need to provide separate optical barriers between the IRED and the detector, which makes it much easier to create robust, uncomplicated solutions for different setups.
Since the SFH 7776 covers the complete working range from 0 to 16 mm it would even react to direct contact (“zero distance detection”). The touch function of the display is therefore reliably deactivated even in marginal situations.
“Overall, the SFH 7776 overcomes various challenges in terms of proximity and ambient light detection in the component itself, so designers can integrate the product in smartphones relatively easily”, adds Dirk Sossenheimer.
Technical data SFH 7776: Dimensions 4 x 2.1 x 1.35 mm
Current draw in standby mode 0.8 μA Sensitivity of the ambient light signal
0.002 to 68,000
lx Working distance of proximity sensor max. 16 cm
Hitachi Cable launching GaN template for LEDs
At CS Mantech 2013, Hitachi Cable will present its gallium nitride based templates grown on sapphire
Hitachi Cable has developed a new mass-production technology for GaN-templates as shown in Figures 1 and 2 below.
All these crystal layers are produced by the MOVPE processes. The MOVPE method is suitable for growing active layers which require atomic-level control of the film thickness.
Meanwhile, a disadvantage of this method is that it takes a long time to grow a high-quality and thick n-type GaN layer. White LED epiwafers can be grown about once or twice a day at the most, and thus there is a need for a high-efficiency production method.
To solve this problem, Hitachi Cable developed a GaN- template used as a base substrate for growth in the MOVPE method.
The process allows high-quality GaN single-crystal thin film to be grown on a sapphire substrate and the company plans to start selling these templates.
The GaN template consists of an n-type GaN layer grown on a sapphire substrate. Using a GaN-template means
June 2013
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Therefore, this product is expected to become an effective solution to improve the position of white LED manufacturers in the industry, where there is severe competition.
The demand for white LEDs is rapidly expanding and they have come to be used in backlight unit in liquid crystal displays (LCDs) and ordinary lighting devices in recent years thanks to their energy efficiency and long service life.
The structure of an white LED epiwafer consists of a thin active layer and a p-type GaN layer with a total thickness of about 1μm over an n-type GaN layer with a thickness of about 10μm, grown on a sapphire substrate as shown in Figure 3 below.
Using this product as a base substrate for an epitaxial wafer for white LEDs the company claims it makes it possible to drastically improve productivity of white LED epiwafers and the LED properties.
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