What is diffusion length?
What is diffusion length?
The diffusion length of a carrier type in a material can be defined as the average distance that an excited carrier will travel before recombining. The diffusion length can be defined as follows: L D = Dτ , where D is the diffusion coefficient and τ is the lifetime of the excited carrier.
What is diffusion length formula?
The following calculator provides a way of converting between lifetime and diffusion length using more familiar units. The diffusivity can be found in the appendices. Minority carrier lifetime, τb= µsec Minority Carrier Diffusivity, D = cm²/s. Minority carrier diffusion, L= µm.
What is the diffusion length for electrons when DN 10 cm 2 s and t 40s?
20cm
What is the diffusion length for electrons when Dn=10cm2/s and τn=40s? =20cm.
What is diffusion length physics?
The diffusion length is the average distance that the excess carriers can cover before they recombine. Diffusion length depends on the lifetime and mobility of the carriers. For the resolution of every electrical measurement the diffusion length is the limitation.
What is the characteristic diffusion length?
The diffusion length is the characteristic length scale for diffusion problems. It increases as the square root of the time. For semi-infinite regions, the solution looks the same for all times if the length is scaled by the appropriate diffusion constant for that time.
What is meant by diffusion current?
Diffusion Current is a current in a semiconductor caused by the diffusion of charge carriers (holes and/or electrons). This is the current which is due to the transport of charges occurring because of non-uniform concentration of charged particles in a semiconductor.
What is neutron diffusion length?
The physical meaning of the diffusion length, L, can be seen by calculation of the mean square distance that a neutron travels in the one direction from the plane source to its absorption point.
How do you calculate characteristic diffusion length?
For particle diffusion in one dimension, you may think of the particle as jumping around on the x-axis. Some times it jumps to the right, and some times to the left. The end result is that it typically takes τ=L2/D to cover the distance L, when the diffusion constant is D.
How diffusion current is created?
Diffusion current is a current in a semiconductor caused by the diffusion of charge carriers (holes and/or electrons). This is the current which is due to the transport of charges occurring because of non-uniform concentration of charged particles in a semiconductor.
What is fast neutron diffusion?
We have characterized the effects of the global distribution of neutrons simply by a nonleakage probability (thermal or fast), which as stated earlier increases toward a value of one as the reactor core becomes larger. Solution of diffusion equation in multiplying system with a control rod insertion.
What is neutron diffusion equation?
The neutron diffusion equation is a basic balance equation that describes the transport of neutrons in space, energy, and time. The establishment of the balance equation makes a direct use of the concepts of neutron flux and current as well as effective cross section.
Why is the diffusion length of silicon so high?
The percentage refers to the fraction of light-generated carrier and the variations between one region and another are due to variations in the diffusion length in the solar cell caused by the grain boundaries in the multicrystalline material. In silicon, the lifetime can be as high as 1 msec.
Is the diffusion of dopants in Silicon simple?
Some of the dopants that diffuse in silicon do not fall into the simple category. For example, boron can described reasonably well with the simple theory, but phosphorus cannot. Lastly, we should note the diffusion can occur in all three dimensions, so the general 3-D form of the simple diffusion eq. is 1 W = ‘ 1 [\
How is diffusion time independent of system size?
If the diffusion length is much longer than the system size, the profiles of concentration must be essentially linear, and are independent of time (if diffusion is the only thing happening). A change in one part of the reactor is reflected throughout the reactor in a diffusion time (L 2 /4D).
What happens when the diffusion constant is scaled?
For semi-infinite regions, the solution looks the same for all times if the length is scaled by the appropriate diffusion constant for that time. However, for real finite systems (like chemical vapor deposition reactors) the behavior of solutions changes qualitatively depending on how large the system is in comparison to the diffusion length.
What is diffusion length? The diffusion length of a carrier type in a material can be defined as the average distance that an excited carrier will travel before recombining. The diffusion length can be defined as follows: L D = Dτ , where D is the diffusion coefficient and τ is the lifetime of the…