Avalanche Breakdown-Double Injection Induced Negative Resistance in Semiconductors

Abstract

Current-controlled negative resistances have been observed in a variety of point-contact Ge diodes. Experiments were done at 300°K and 243°K, using both dc and pulsed currents. In these experiments both contacts are of the ohmic, non-injecting type. The effect has been seen in both n and p -type Ge single crystals having resistivities that range from 0.1 to 50 ohm-cm. The frequency of the relaxation oscillations resulting from the negative resistance has ranged from 1 KG to 10 MC depending on the cathode-anode spacing and the external capacitance used. Analysis shows that thermal effects can not explain these results. The negative resistance is believed to be due to the two carrier current flow (double injection) in the bulk material after avalanche injection has been produced at the point contact. This explanation for the negative resistance differs from those previously proposed and allows predictions of the I-V curve as well as frequency limitations. Experiments with different sized points, varying pulse widths and magnetic fields are described and analyzed in terms of the above model.