The luminous efficiency of LED is a main factor to measure whether the photoelectric convertor is efficiency. How to improve the luminaries efficiency. This article introduces effect way to improve the luminaries efficiency of LED from metal film reflection technology.
If the transparent substrate technology is first from HP, Lumileds etc. in USA, then the metal film reflection technology is main abundantly researched and developed by the companies in Japan and Taiwan. This technology not only avoids the patent of transparent substrate,but also more conducive to mass production. So to speak, its effect is the same with the transparent substrate technology. The technology is usually called the MB technology. Firstly, remove the substrate of GaAs, then vapor the metal film of AL on its surface and the basal surface of Si, then weld together under certain temperature and pressure. In this way, the light that is from luminous layer to baseboard is reflected by the metal film of AL to the surface of the chip, thereby makes the luminaries efficiency of the device increased by 2.5 times.Experimental results show that the type of MB red LED, when the current is 400mA and 800mA,the luminous can reach to 37lm and 7 lm respectively. This kind of device has been into the small batch production in SANKEN,Guolian,Quanxin. Compared with the traditional devices, the luminaries efficiency has been improved to a great extent. In addition to the MB structure of devices,Guolian also develops a kind of high light InGaAIP LED,a new generation device called GB.The so-called GB is short for Giga Bright. The technology adopts a new type of cellophane tape, bonding the LED epitaxial slice that has the absorption of substrate of GaAs and a piece of sapphire substrate, then remove the absorption of substrate of GaAs and make electrode in epitaxial layer, thus access to a high luminous efficiency.
