3 Haynes-Shockley Experiment

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Run and watch the real space display. You see first that the electrons begin to disperse due to diffusion, but soon you notice a drift to the left resulting from the applied field. By switching the position graph between average and deviation you see a quantitative measure of both the drift and the diffusion. (Remember that the deviation plot gives the mean SQUARE deviation.)

These two aspects of electron transport are dramatically illustrated in semiconductors by the Haynes-Shockley experiment in which a pulse of minority carriers is injected at one point in a crystal and monitored with a second probe downstream. The pulse width and pulse delay time give independent measures of the diffusion constant and the mobility.