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.
|Published (Last):||2 May 2011|
|PDF File Size:||6.56 Mb|
|ePub File Size:||10.87 Mb|
|Price:||Free* [*Free Regsitration Required]|
Example of collected pulses with different values of sweep voltage. 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 Haynes-Shockley experiment requires not included: The measurement of the time of flight t. Setup of the original H-S apparatus. The second pulse corresponds to the excess electon distribution passing under the collector contact: In our new setup the excess carriers are optically injected using internal photoelectric effect shodkley the need of a reliable point-contact emitter.
From Wikipedia, the free encyclopedia. Shkckley version of the Haynes-Shockley experiment. The main difficulties are in the sample preparation, in the charge shokcley and in the signal detection. To see the effect, we consider a n-type semiconductor with the length d. Views Read Edit View history.
In the experiment, a piece of semiconductor gets a pulse of holesfor example, as induced by voltage or a short laser pulse.
Haynes–Shockley experiment – Wikipedia
The semiconductor behaves as if there were only holes traveling in it. 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 hsynes conceptually simple. Block diagram of the apparatus with optical injection. Optional N-doped Germanium sample with ohmic contacts.
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 exxperiment the first one. This page was last edited on 21 Marchat LCD display measuring the flight distance, the sweep voltage and the laser intensity.
P-doped Germanium sample with ohmic contacts. We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. Switchable polarity fpr P-doped and N-doped samples. Block diagram of the apparatus with optical injection The measurement of the time of flight t. Sample Holder with double glider for optical fiber motorized and for point contact.
The point contacts are partially rectifying and therefore they are drawn as diodes in figure shocjley 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.
The first peak is simultaneous with the injection pulse: We consider the continuity equation:.
A simple and instructive version of the Haynes-Shockley experiment
Double pulser for the sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal.
Bell System Technical Journal. In the following, we reduce the problem to one dimension. 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:. The sample-holder with two gliders for optical fiber and point contact collector. The two initial equations write:. Holes then start to travel towards the electrode where we detect them.
shocklye 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. Moreover the electrons recombine with holes so that their hynes decreases exponentially with time t as: Circuitry for testing the rectifying behavior of the point contact I-V curves.
The block diagram of the original Haynes and Shockely experiment is shown in Fig. Java Applets simulations of the Haynes-Shockley signal: Subscript 0s indicate equilibrium concentrations. In semiconductor physicsthe Haynes—Shockley experiment was an experiment that demonstrated that diffusion of minority carriers in a semiconductor could result in a current.
The first term shoc,ley the equations is the drift currentand the second term is the diffusion current. 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.
Simulation 1 Simulation 2. The experiment proposed in by J.