Tuesday, December 22, 2009

Taiwanese Scientists Discover Low Cost & Green Method for Making Red-Light Emitting Diodes with Silicon Quantum Dots

Model Broad Agency Announcement (BAA)
Atomic Energy Council - Institute of Nuclear Energy Research (INER) (Taouyuan, TW) researchers Tsun-Neng Yang and Shan-Minga Lan discovered an environmentally friendly and economical method for manufacturing a red-light emitting diode (red-light LED) with a light emitting silicon (Si) base material that has Si quantum dots as luminescence centers, according to U.S. Patent 7,635,603

The manufacturing process produces red-light LEDs with economy, environmental protection and high efficiency. The LED luminescent strength is enhanced covering the whole red-light zone of a white-light spectrum. It can be produced at low cost, in a manner that is harmlessness to the environment and in a manner compatible with semiconductor manufacturing techniques. material.

The INER method for making a red-light LED with Si quantum dots involves a Si-rich non-stoichiometric silica film covering on a substrate that is grown through  atmospheric pressure chemical vapor deposition (APCVP). Then, an annealing treatment to the substrate is processed to obtain a phase separation in the non-stoichiometric silica film so that a silica film having Si quantum dots as luminescence centers (Si QDs-SiO2 film) is formed on the substrate; and, then, the Si QDs-SiO2 film is put into a vacuum stove for a surface treatment under a temperature between 700 and 1000 Celsius degrees in an environment of oxygen gas added with graphite. Accordingly, a novel method for making a red-light LED having Si quantum dots is obtained.

In the early 1960s, a first red-light LED using a ternary alloy of GaAsP was successfully obtained. In 1980s, a LED using AlGaAs was successfully developed with enhanced light emitting efficiency. In 1990s, Hewlett-Packard Co. and Toshiba Co. further developed a LED with high efficiency using a quaternary alloy of AlGaInP. Yet, the manufactures of these ternary or even quaternary alloys are complex and the materials used include some rare or even poisonous heavy metals, such as Ga, As, P, etc.

The above prior arts use ternary or quaternary alloys to obtain red-light LEDs; but those ternary or quaternary alloys are rare or poisonous heavy metals at the same time. The prior arts do not  provide low-cost, environmentally friendly means for manufacturing low cost red LEDs.

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