Ion Drift in an <i>n-p</i> Junction

If a reverse bias is applied to an n-p junction at a sufficiently elevated temperature to give either the donor or the acceptor ions appreciable mobility, the ions will drift in the electric field of the junction to produce an intrinsic semiconductor region between the n and p regions. Such ion drift offers a simple and straightforward method for investigating diffusion constants, as well as chemical interactions within the host lattice which affect this diffusion. Preliminary results indicate its feasibility for measuring the diffusion constant of Li in Si to as low as 10−18 cm2/sec and also for measuring the effect of Li-oxygen and Li-acceptor interactions in decreasing the diffusion rate. Intrinsic regions resulting from ion drift have been used to produce diodes with breakdown in excess of 4000 volts from low resistivity silicon. In addition, they can be used to extend the frequency range of devices by virtue of the decrease in junction capacitance associated with such an incorporated intrinsic region. Ion drift has also been used for the fabrication of analog transistors, an early unit having an input impedance of 6 megohms, a power gain of 17 db and a voltage gain of 4.

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