GaAs solar cell dopant concentration
Impurity semiconductors: Impurity semiconductors can be obtained by doping a small amount of impurity elements into intrinsic semiconductors through diffusion process.
According to the doped impurity elements, N-type semiconductors and P-type semiconductors can be formed; control the concentration of doped impurity elements to control the conductivity of the impurity semiconductors.
N-type semiconductors: Pure silicon crystals are doped with pentavalent elements (such as phosphorus) to replace the positions of silicon atoms in the crystal lattice to form N-type semiconductors.
Another factor that has obvious influence on UOC is the doping concentration of semiconductor. The higher the doping concentration is, the higher the UOC is. However, when the impurity concentration in silicon is higher than 1018 / cm3, it is called high doping. The phenomena such as band gap contraction, incomplete ionization of impurities and decrease of minority carrier lifetime caused by high doping are called high doping effect, which should also be avoided.
Since the outermost layer of impurity atoms has five valence electrons, in addition to forming a covalent bond with the surrounding silicon atoms, there is one more electron. The extra electrons are not bound by covalent bonds and become free electrons. In N-type semiconductors, the concentration of free electrons is greater than the concentration of holes, so free electrons are called majority carriers, and holes are minority carriers. Because impurity atoms can donate electrons, they are called donor atoms.
Gallium is a dopant used in 8-14 μ A long wavelength infrared photoconductive silicon detector in an atmospheric window of 1.5m. GA doped silicon is also promising for solar cells, because it has a long minority carrier life and will not reduce the life; Therefore, it becomes more and more important as a substitute for boron doped substrate in solar cell applications.