Optoelectronic Semiconductor Devices Principals and Characteristics

8 DEVICE FABRICATION 
For the devices discussed in the previous sections various kinds of technologies required. These 
optoelectronic devices are made of semiconductor materials, packaged, installed, and then used in 
equipment and systems. 
Each technology influences the performance of the device. The device characteristics depend on the 
quality of semiconductor crystal, the surface and interface state density, parasitic capacitance of package, 
etc. 
8.1 CRYSTAL GROWTH 
Crystal growth is the first step in device fabrication. There are different techniques that are used 
depending on the costs and needs for the quality of the crystal. 
8.1.1 
LIQUID-PHASE EPITAXY
 
Used in making various semiconductor devices, and the crystal growth occurs near thermal equilibrium. 
When a supersaturated solution of semiconductor material comes into contact with a single-crystalline 
substrate, a lattice-matched epitaxial layer grows on the substrate. For forming multilayer structures such 
as DHs, graphite sliders often used. The substrate set on the slide in a quartz reactor and lid under the 
solutions corresponding to each layer (see Figure 
36.
). 
Figure 36.: Basic setup for LPE. [4] 
A flow of H
2
prevents oxidation of the solutions and the substrate, and the growth is terminated by sliding 
the substrate out from under the solution. Extremely important the control of the temperature for the 
growth rate, crystal quality. (Example: for the length of about 30 cm, the temperature in the reactor must 
be controlled with a precision of about ±0.1ºC.) 
The thickness of a grown layer is determined by the temperature and the length of time in which the 
substrate and solution are in contact. 
 
 

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