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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Moreover the electrons recombine with holes so that their number decreases exponentially with time t as: Bell System Technical Journal.
Haynes–Shockley experiment – Wikipedia
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. Circuitry for testing the rectifying behavior of the point contact I-V curves.
We consider the continuity equation:. In the following, we reduce the problem to one dimension. Views Read Edit View history. P-doped Germanium sample with ohmic contacts. The semiconductor behaves as if there were only holes traveling in it.
Optional N-doped Germanium sample with ohmic contacts. Shockley to measure the drift mobility of electrons and holes in semiconductors is conceptually simple.
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Block diagram of the apparatus with optical injection. 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.
This can be interpreted as a Dirac delta function that is created immediately after the pulse. Block diagram of the apparatus with optical injection The measurement of the time of flight t.
Switchable polarity fpr P-doped and N-doped samples. In semiconductor physicsthe Haynes—Shockley experiment was an experiment that demonstrated that diffusion of minority carriers in a semiconductor could result in a current. From Wikipedia, the free encyclopedia.
A simple and instructive version of the Haynes-Shockley experiment
We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. This electron pulse will drift, under the electric field action, with velocity v dand after some time t it will reach the region underlying the electrode C collector. The two initial equations write:. As edperiment example, let us consider a P-doped semiconductor bar, of length lwith ohmic contacts soldered at both ends Inside the sample an electric field named sweep field E s is temporarily produced by a pulsed generator, sketched in Figure 1 as a battery in haynea with a switch.
The experiment proposed in by J. The Haynes-Shockley experiment requires not included: The point contacts are partially rectifying and therefore they are drawn as diodes in figure 1 By applying to the electrode E emitter a short negative pulse voltage with an amplitude large enough to hahnes bias the diode D Exprrimentelectrons will be injected into the crystal region underlying the emitter.
In the experiment, a piece of semiconductor gets a pulse of holesfor example, as induced by voltage or a short laser pulse. New version of the Haynes-Shockley experiment.
When the excess electron pulse haynrs the point contact C, the minority charge carrier density is locally increased, thus increasing the inverse current and producing a voltage drop across the resistance R. In our new setup the excess carriers are optically injected using internal photoelectric effect avoiding the need of a reliable point-contact emitter.
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:.
Holes then start to travel towards the electrode where we detect them. Two point contacts electrodes E and C are made by two metal needled separated by a distance d.
Simulation 1 Simulation 2. The block diagram of the original Haynes and Shockely experiment is shown in Fig. The experiment was reported in a short paper by Haynes and Shockley in with a more detailed version published by Shockley, Pearson, and Haynes in Double pulser for the sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal.
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