The Haynes-Shockley technique for the measurement of electron and hole drift mobility mu in semiconductors is here presented in a version suitable for an. The Haynes-Shockley Experiment. Minority carrier applet and tutorial, which describes generation by laser pulse, diffusion due to nonuniform concentration, drift. The ambipolar drift mobility of holes in n‐type HgCdTe with nominal composition of x= was determined by the Haynes–Shockley experiment.
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Circuitry for testing the rectifying behavior of the point contact I-V curves. Experument experiment was reported in a short paper by Haynes and Shockley in with a more detailed version published by Shockley, Pearson, and Haynes in In the following, we reduce the problem to one dimension. In our new setup the excess carriers are optically injected using internal photoelectric effect avoiding the need of a reliable point-contact emitter. The injected electrons in fact, while drifting towards the collector, diffuse broadening their spatial distribution, so that the width of the collected pulse increases with the time of flight t.
This electron pulse will drift, under the experiiment field action, with velocity v dand after some time experimnet it will reach the region underlying the electrode C collector. P-doped Germanium sample with ohmic contacts. Double pulser for the hagnes voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal. The second pulse corresponds to the excess electon distribution passing under the collector contact: The first peak is simultaneous with the injection pulse: It is an experiment with great educational value, because it allows direct investigation of the drift velocity, of the diffusion process and of the recombination of excess charge carriers.
Holes whockley start to travel towards the electrode where we detect them.
Example of collected pulses with different values of sweep voltage. The Haynes-Shockley experiment requires not included: From Wikipedia, the free encyclopedia.
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Shockley to measure the drift mobility of electrons and holes in semiconductors is conceptually simple. Switchable polarity fpr P-doped and N-doped samples.
The two initial equations write:. The block diagram of the original Haynes and Shockely experiment is shown in Fig.
We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. Block diagram of the apparatus with optical injection The measurement of the time of flight t.
A simple and instructive version of the Haynes-Shockley experiment – IOPscience
The signal then is Gaussian curve shaped. However, as electrons and holes diffuse at different speeds, the material has a local electric charge, inducing an inhomogeneous electric field which can be calculated with Gauss’s law:. Experimwnt consider the continuity equation:. LCD display measuring the flight distance, the sweep voltage and the laser intensity.
Haynes–Shockley experiment – Wikipedia
To see the effect, we consider a n-type semiconductor with the length d. New version of the Haynes-Shockley experiment. Views Read Edit View history. The measurement of the time of flight t.
Subscript 0s indicate equilibrium concentrations. hayynes
This page was last edited on 21 Marchat Optional N-doped Germanium sample with ohmic contacts. The main difficulties are shockey the sample preparation, in the charge injection and in the signal detection.
Two point contacts electrodes Shocklwy and C are made by two metal needled separated by a distance d. On the oscilloscope screen we may observe a first short negative pulse, with amplitude comparable to that of the injection pulse and, after some delay ta second negative pulse, wider and much smaller than the first one.
This can be interpreted as a Dirac delta function that is created immediately after the pulse. Simulation 1 Simulation 2. The sample-holder with two gliders for optical fiber and point contact collector.