Chemistry Reference
In-Depth Information
All commercially available LEDs in the visible to the infrared
range (i.e., 450-1500 nm) are made of semiconductor thin films of
compounds consisting of elements from group three and five in the
periodic table (III-V semiconductors) [26]. Group three elements
include aluminum, gallium, and indium, while group five elements
include nitrogen, phosphorus, and arsenic. Common compounds
include GaN and InGaN.
As shown in Fig. 6.2, LED is typically made up of three layers
of different materials [24, 27]. The base layer is an n-type material
(e.g., GaN doped with Si) with a high concentration of free electrons,
followed by multiple alternating thin layers of materials with smaller
bandgap known as quantum wells. The top layer is a p-type material
(e.g., GaN doped with Mg) with a high concentration of holes. The
region with smaller bandgap sandwiched between the two layers
of larger bandgap materials creates a region where the holes and
electrons may recombine, emitting light with the wavelength of the
smaller bandgap material.
Figure 6.2
Structure of a typical GaN-based LED [25].
