Low-Density Injected Plasma in p-Type Indium Antimonide

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Abstract
Properties of low‐density injected plasma in p‐InSb have been studied. Measurements have been made on n+‐p‐p+ diodes biased in the forward direction at 77°K. The time dependent behavior of the I‐V characteristics has been measured by application of dc pulses, with and without a transverse magnetic field present. At short periods after applying the pulses, or at low injection levels, the current is carried mainly by holes in the major part of the sample. At long periods after applying the pulses and at high injection levels the shape of the I‐V characteristics is governed by the injected plasma, and a steady state is reached within about 10 μsec. In a transverse magnetic field the plasma is deflected by the Suhl effect towards the surface. There the electrons and holes recombine at a high rate. This mechanism reduces the number of carriers which contribute to conduction. At a magnetic field of about 300 G the I‐V curves have a similar shape as the ones measured at a short period after applying the pulse. Trapping and recombination mechanisms which are very important for a low‐density plasma in p‐type InSb have been studied by measuring the conductivity modulation after the end of the injecting pulse. The occurrence of an S‐shaped I‐V characteristic is due to the filling of the traps with injected electrons. The measurement of the conductivity modulation in connection with fourpoint probe measurements show that already at low currents, below the NDR region, traps are filled within a small channel. Its cross section decreases with increasing distance from the injecting contact. With increasing current the channel grows and reaches a maximum of about half of the sample cross section in the region above negative differential resistivity.

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