A thin P-type silicon sample is uniformly illuminated with light which...
Recombination rate, R = B(nn0 + nn)(Pn0 + Pn)Electron and hole concentrations respectively under thermal equilibrium nn0 & Pn0 Excess elements and hole concentrations respectively. Thus, option B is the correct answer.
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A thin P-type silicon sample is uniformly illuminated with light which...
The correct answer is option 'D', which states that the recombination rate is directly proportional to the excess minority carrier concentration. Let's understand why this is the correct answer.
Recombination in a semiconductor occurs when an electron from the conduction band recombines with a hole in the valence band. This process leads to the annihilation of both the electron and the hole, resulting in a decrease in the concentration of both charge carriers.
In a P-type semiconductor, the majority carriers are holes, while the minority carriers are electrons. When the P-type silicon sample is uniformly illuminated with light, excess electron-hole pairs are generated due to the absorption of photons by the semiconductor. These excess carriers are the minority carriers.
Now, let's analyze the given options to find out which one is directly proportional to the recombination rate:
a) The minority carrier mobility: The mobility of carriers determines how fast they can move through the material under the influence of an electric field. However, the mobility does not directly affect the recombination rate. Therefore, option 'a' is incorrect.
b) The minority carrier recombination lifetime: The recombination lifetime represents the average time it takes for a minority carrier to recombine with a majority carrier. It is inversely proportional to the recombination rate. Therefore, option 'b' is incorrect.
c) The majority carrier concentration: The majority carrier concentration in a P-type semiconductor is the concentration of holes. However, the recombination rate is not directly influenced by the majority carrier concentration. Therefore, option 'c' is incorrect.
d) The excess minority carrier concentration: This option states that the recombination rate is directly proportional to the excess minority carrier concentration. When excess minority carriers are present, there is a higher probability of recombination events occurring, leading to a higher recombination rate. Therefore, option 'd' is correct.
In conclusion, the correct answer is option 'd' because the recombination rate is directly proportional to the excess minority carrier concentration.