Tunneling Spectroscopy and Band-Structure Effects innGaSb under Pressure

The effect of hydrostatic pressure (up to 16 kbar) on the characteristics of $n$-type-GaSb-Pb tunnel contacts has been investigated both experimentally and theoretically. The background resistance $\frac{\mathrm{dV}}{\mathrm{dI}}$ exhibits huge changes when the $〈000〉$- and $〈111〉$-conduction-band extrema cross each other. In the indirect-gap configuration, the tunnel current results from four contributions: (i) the specular component corresponding to the $〈111〉$ valleys, (ii) beyond a negative threshold voltage, an additional specular part related to the $〈000〉$ minimum which leads to a direct measurement of the interband energy gap, (iii) a phonon-assisted current which provides the first determination of zone-edge phonon energies in the $〈111〉$ directions, and (iv) an impurity-assisted mechanism. Application of pressure in GaSb constitutes an original way of continuously varying the Fermi degeneracy. This has some striking influence on the line shape, parity, magnitude, and position of phonon structures displayed by the tunneling characteristics.