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 first term of the equations is the drift currentand the second term is the diffusion current. Retrieved from ” https: 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. 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.
New version of the Haynes-Shockley experiment. In our new setup the excess carriers are optically injected shocklwy internal photoelectric epxeriment avoiding the need of a reliable point-contact emitter. Holes then start to travel towards the electrode where we detect them. The measurement of the time of flight t. 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 the resistance R.
A simple and instructive version of the Haynes-Shockley experiment
Setup of the original H-S apparatus. LCD haaynes measuring the flight distance, the sweep voltage and the laser intensity. Circuitry for testing the rectifying behavior of the point contact I-V curves.
haynex From Wikipedia, the free encyclopedia. This can be interpreted as a Dirac delta function that is created immediately after the pulse. 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:.
In the following, we reduce the problem to one dimension. The main difficulties are in the sample preparation, in the charge injection and in the signal detection. Double pulser for yaynes sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal.
Bell System Technical Journal. Simulation 1 Simulation 2.
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.
This page was last edited on 21 Marchat 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. The signal then is Gaussian curve shaped. The Haynes-Shockley experiment requires not included: Two point contacts electrodes E and C are made by two metal needled separated by a distance d.
Shockley to measure the drift mobility of electrons and holes in semiconductors is conceptually simple. The second pulse corresponds to the excess electon distribution passing under the collector contact: We are interested in determining the mobility of the carriers, diffusion constant and relaxation time.
Java Applets simulations of the Haynes-Shockley signal: Sample Holder with double glider for optical fiber motorized and for point contact.
The block diagram of the original Haynes and Shockely experiment is shown in Fig. Views Read Edit View history. The semiconductor behaves as if there were only holes traveling in it.
P-doped Germanium sample with ohmic contacts. Optional N-doped Germanium sample with ohmic contacts. To see the effect, we consider a n-type semiconductor with the length d. 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.
Expediment diagram of the apparatus with optical injection The measurement of the time of flight t. 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 Shockleh Eelectrons will be injected into the crystal region underlying the hxynes.