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市售的GaAsP发光二级管所发出的光仅占其内部所产生光量的2～4％。效率低的部分原因是由于光被较小的带隙过渡区和衬底所吸收。假如GaAsP生长在透明衬底上,从而使衬底和过渡区具有比GaAsP发射区更宽的带隙,则外量子效率可获得显著的提高。原则上诸如尖晶石、蓝宝石、GaP以及带隙比发光GaAsP更大的GaAsP材料都可用作衬底。虽然对于后两种材料都进行过研究, 但本文的结果都是用GaP作衬底制作的器件所得到的。 所研究过的第一种结构是在GaP(100)衬底上生长GaAs0.6P0.4。外延层组分从衬底的GaP开始逐渐变化到GaAs0.6P0.4,紧接着再生长5μ恒定组分的GaAs0.6P0.4。器件的几何构造是采用Zn扩散和光刻腐蚀的p-n结台面,顶部是Al欧姆接触,底部是能反射光的欧姆接触。然后经过锯割或划片把片子分成小块,由于GaAs0.6P0.4是直接带发射体。恒定组分区p-n结所产
Commercially available GaAsP LEDs emit only 2-4% of the amount of light they generate internally. Part of the inefficiency is due to light being absorbed by the smaller bandgap transition region and substrate. If GaAsP is grown on a transparent substrate so that the substrate and the transition region have a wider bandgap than the GaAsP emission region, a significant increase in external quantum efficiency can be obtained. In principle, such as spinel, sapphire, GaP and GaAsP materials with a larger band gap than GaAsP can be used as the substrate. Although the last two materials have been studied, but the results of this paper are made with GaP substrate device obtained. The first structure studied has been the growth of GaAs0.6P0.4 on a GaP (100) substrate. The epitaxial layer composition gradually changes from GaP of the substrate to GaAs0.6P0.4, followed by growth of a 5μ constant component of GaAs0.6P0.4. The geometry of the device is a p-n junction with Zn diffusion and photolithography, with Al ohmic contacts on top and ohmic contacts on the bottom that reflect light. Then after sawing or dicing the film is divided into small pieces, since GaAs0.6P0.4 is a direct emitter. Constant component p-n junction produced