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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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. New version of the Haynes-Shockley experiment.
To see the effect, we consider a n-type semiconductor with the length d. Circuitry for testing the rectifying experimemt of the point contact I-V curves. Double pulser for the sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal. Retrieved from ” https: When the excess electron pulse reaches the point contact Hayjes, the minority charge carrier density is locally increased, thus increasing the inverse current and producing a voltage drop across the resistance R.
Example of collected pulses with different values of sweep voltage. 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. The measurement of the time of flight t. The main difficulties are in the sample preparation, in the charge injection and in the signal detection. The experiment proposed in by J.
Views Read Edit View history. Setup of the original H-S apparatus. Simulation 1 Simulation 2. 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. Holes then start to travel towards the electrode where we detect them. In the experiment, a piece of semiconductor gets a pulse of holesfor example, as induced by voltage or a short laser pulse.
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. 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:.
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The signal then is Gaussian curve shaped. Switchable polarity fpr P-doped and N-doped samples. Subscript 0s indicate equilibrium concentrations. Block diagram of the apparatus with optical injection The measurement of the time of flight t.
Haynes–Shockley experiment – Wikipedia
On ecperiment 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. 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.
Sample Holder with double glider for optical fiber motorized and for point contact. In semiconductor physicsthe Haynes—Shockley experiment was an experiment that demonstrated that diffusion of minority carriers in a semiconductor could result in a current.
Block diagram of the apparatus with optical injection. The second pulse corresponds to the excess electon distribution passing under the collector contact: Moreover the electrons recombine experimeng holes so that their number decreases exponentially with time t as: 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 In our new setup the excess carriers are optically injected using internal photoelectric effect avoiding the need of a reliable point-contact emitter.
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