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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The signal then is Gaussian curve shaped. 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.
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:. This page was last edited on 21 Marchat 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. The block diagram of the original Haynes and Shockely experiment is shown in Fig.
The semiconductor behaves as if there were only holes traveling in it. The two initial equations write:.
A simple and instructive version of the Haynes-Shockley experiment – IOPscience
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. The second pulse corresponds to the excess electon distribution passing under the collector contact: To see the effect, we consider a n-type semiconductor with the length d.
As an 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 series with a switch.
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.
A simple and instructive version of the Haynes-Shockley experiment
New version of the Haynes-Shockley experiment. Setup of the original H-S apparatus. LCD display measuring the flight distance, the sweep voltage and the laser intensity.
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 forward bias the diode D Eelectrons will be injected into the crystal region underlying the emitter. This can be interpreted as a Dirac delta function that is created immediately after the pulse.
The first term of the equations is the drift currentand the second term shocklwy the diffusion current. In the experiment, a xhockley of semiconductor gets a pulse of holesfor example, as induced by voltage or a short laser pulse.
Shockley to measure the drift mobility of electrons and holes in semiconductors is conceptually simple. Moreover the electrons recombine with holes so that their number decreases experiemnt with time t as: In our new setup the excess carriers are optically injected using internal photoelectric effect avoiding the need of a reliable point-contact emitter. We consider the continuity equation:. When the excess electron pulse reaches the point contact C, the minority charge carrier density is locally increased, thus increasing the inverse current and producing a voltage drop across shockleey resistance R.
Sample Holder with double glider for optical fiber motorized and for point contact. In the following, we reduce the problem to one dimension.
Bell System Technical Journal. We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. The first peak is simultaneous with the injection pulse: Block diagram of the apparatus with optical injection The measurement of the time of flight t. Circuitry for testing the rectifying behavior of the point contact I-V curves. P-doped Germanium sample with ohmic contacts. Holes then start to travel towards the electrode where we detect them.
The sample-holder with two gliders for optical fiber and experimenr contact collector. The experiment proposed in by J. The Haynes-Shockley experiment requires not included: Subscript 0s indicate equilibrium concentrations. Java Applets simulations of the Haynes-Shockley signal: Block diagram of the apparatus with optical injection.
Switchable polarity fpr P-doped and N-doped samples.
Haynes–Shockley experiment – Wikipedia
This electron pulse will drift, under the electric field action, with velocity v dand jaynes some time t it will reach the region underlying the electrode C collector. The measurement of the time of flight t. 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.
Two point contacts electrodes E and C are made by two metal needled separated by a distance d. Simulation 1 Simulation 2. Retrieved from ” https: