Recent Developments in LEDs

Here is some more information about the inverted Pyramid LED.
It was described quite recently (M.R. Krames et. al., "High-Power truncated-inverted-pyramid (AlxGa1-x)0.5In0.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency," Applied Physics Letters, 75[16], pp. 2365, (1999)) and has a large optical efficiency leading to a "external quantum efficiency" which is simply the what we called total external efficiency of 55% (as compared to about 30 % of the former champion).
The cross section below shows why: There are few reflection losses. Otherwise the device is not quite as simple as looks like. It is based on an epitaxially-grown aluminum gallium indium phosphide/gallium phosphide (AlGaInP/GaP) multiwell active region sandwiched between an n-type gallium phosphide (GaP) layer and a p-type GaP layer.
CrOss section Ofinverted pyramid LED
More information can be found in a recent article from the internet or in the Scientific American from February 2001.
 

With frame With frame as PDF

go to 7.1.1 Products, Market, Materials, and Technologies

go to 5.1.4 Wavelength Engineering

go to 7.1.2 Some LED Concepts

© H. Föll (Semiconductors - Script)