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):||1 July 2006|
|PDF File Size:||6.3 Mb|
|ePub File Size:||4.42 Mb|
|Price:||Free* [*Free Regsitration Required]|
The first term of the equations is the drift currentand the second term is the diffusion current. Views Read Edit View history. The Haynes-Shockley experiment requires not included: The sample-holder with two gliders for optical hzynes and point contact collector. Block diagram of the apparatus with optical injection.
The two initial equations write:. The semiconductor behaves as if there were only holes traveling in it.
A simple and instructive version of the Haynes-Shockley experiment
To see the effect, we consider a n-type semiconductor with the length d. Block diagram of the apparatus with optical injection Experimdnt measurement of the time of flight t. 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.
Setup of the original H-S apparatus. The first peak is simultaneous with the injection pulse: The second pulse corresponds to the excess electon distribution passing under the collector contact: 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 experimet, wider and expperiment smaller than the first one.
Moreover the electrons recombine with holes so that their number decreases exponentially with time t as: Optional N-doped Germanium sample with ohmic contacts.
Retrieved from ” https: Two point contacts electrodes E and C are made by two metal needled separated by a distance d. When the excess electron pulse reaches the point contact C, the minority yaynes carrier density is locally increased, thus increasing the inverse current and producing a voltage drop across the resistance R.
Double pulser for the sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting the sweep voltage from the collector signal.
Haynes–Shockley experiment – Wikipedia
New version of the Haynes-Shockley experiment. The measurement of the time of flight t. The signal then is Gaussian curve shaped.
Bell Shoxkley Technical Journal. 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 point contacts are partially rectifying and therefore they are drawn as diodes in figure 1 By applying to the shocjley E emitter a short negative shockleu voltage with an amplitude large enough to forward bias the diode D Eelectrons will be injected into the crystal region underlying the emitter.
The main difficulties are in the sample preparation, in the charge injection and in the signal detection. 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. P-doped Germanium sample with ohmic contacts. This can be interpreted as a Dirac delta function that is created expeirment after the pulse. Subscript 0s indicate equilibrium concentrations.
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 semiconductor physicsthe Haynes—Shockley experiment was an experiment that experimnt that diffusion of minority carriers in a semiconductor could result in a current.
We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. In the following, we reduce the problem to one dimension. This page was last edited on 21 Marchat Shockley to measure the drift mobility of electrons and holes in semiconductors is conceptually simple. In the experiment, a piece of semiconductor gets a pulse of holesfor example, as induced by voltage or a shoxkley laser pulse.
The block diagram of the original Haynes and Shockely experiment shokley shown in Fig.