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The saturation current (or scale current), more accurately the reverse saturation current, is the part of the reverse current in a semiconductor diode caused by diffusion of minority carriers from the neutral regions to the depletion region. This current is almost independent of the reverse voltage.
Under reverse bias, the diode equation's exponential term is near 0, so the current is near the somewhat constant reverse current value (roughly a picoampere for silicon diodes or a microampere for germanium diodes, [1] although this is obviously a function of size).
The effect of reverse saturation current on the I-V curve of a crystalline silicon solar cell are shown in the figure to the right. Physically, reverse saturation current is a measure of the "leakage" of carriers across the p–n junction in reverse bias.
The device does not attain its full blocking capability until the reverse current ceases. Reverse biased: For a bias between breakdown and 0 V, the reverse current is very small and asymptotically approaches -I s. For a normal P–N rectifier diode, the reverse current through the device is in the micro-ampere (μA) range.
The Shockley diode equation relates the diode current of a p-n junction diode to the diode voltage .This relationship is the diode I-V characteristic: = (), where is the saturation current or scale current of the diode (the magnitude of the current that flows for negative in excess of a few , typically 10 −12 A).
The mathematical description of the current is provided by the Shockley diode equation. The low current conducted under reverse bias and the large current under forward bias is an example of rectification.
The Shockley equation gives I–V (current-voltage) ... The value of is called the reverse bias saturation current and is defined by: [3] = (+) where h and L ...
Reverse leakage current in a semiconductor device is the current when the device is reverse biased.. Under reverse bias, an ideal semiconductor device should not conduct any current, however, due to attraction of dissimilar charges, the positive side of the voltage source draws free electrons (majority carriers in the n-region) away from the P-N junction.