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. Moreover the electrons recombine with holes so that their number decreases exponentially with time t as: Retrieved from ” https: Switchable polarity fpr P-doped and N-doped samples.
A simple and instructive version of the Haynes-Shockley experiment – IOPscience
Example of collected pulses with different values of sweep voltage. The second pulse corresponds to the excess electon distribution passing under the collector contact: Subscript 0s indicate equilibrium concentrations.
Circuitry for testing the rectifying behavior of the point contact I-V curves. 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 first peak is simultaneous with the injection pulse: The two initial equations write:.
The signal then is Gaussian curve shaped. The main difficulties are in the sample preparation, in the charge injection and in the signal detection. The Haynes-Shockley experiment requires not included: In our new setup the excess carriers are optically injected using internal photoelectric effect avoiding the need of a reliable point-contact emitter.
P-doped Germanium sample with ohmic contacts. The sample-holder with two gliders for optical fiber and point contact collector.
A simple and instructive version of the Haynes-Shockley experiment
Setup of the original H-S apparatus. Optional N-doped Germanium sample with ohmic contacts. Double pulser for the sweep voltage and for the laser-driving pulse, with a differential amplifier subtracting dhockley sweep voltage from the collector signal. 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 shocckley diode D Eelectrons will be injected into the crystal region underlying the emitter.
Bell System Technical Journal. 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.
Two point contacts electrodes E and C are made by two metal needled separated by a distance d. 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 shocklye calculated with Gauss’s law:.
We are interested in determining the mobility of the carriers, diffusion constant and relaxation time. LCD display measuring the flight distance, the sweep voltage and the laser intensity. 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 shcokley.
The semiconductor behaves as if there were only holes traveling in it. Holes then start to travel towards the electrode where experimfnt detect them. The experiment proposed in by J.