Direct and Indirect Tunneling in Germanium at Different Temperatures

Abstract

The current—voltage characteristics of narrow germanium p—n junctions, measured for reverse biases at 4.2°, 77°, 195°, and 298°K, are in agreement with the usual tunneling probability expressions. The reverse current increases at the onset of the direct tunneling transition, that is, in addition to the indirect transition at lower biases. The onset voltage shifts from −0.121 V at 4.2°K to −0.082 V at 298°K in agreement with the band shift in germanium and the smeared-out carrier distribution around the Fermi level. The absolute value of the onset voltage is within 16% of the calculated voltage. The slope d ln(J/V)/dV is −11 (V)−1 for a typical junction; the constant field approximation gives −7 (V)−1.