Electrical properties of GaSb Schottky diodes and p-n junctions

The electrical properties of Schottky diodes and p-n junctions on GaSb ((100), doped with 2 × 1017 cm−3 tellurium) were examined. Capacitance-voltage measurements at 300 K show barrier heights of0.65 eV (Al), 0.6 eV (Au, In, Pd), 0.5 eV (Ga) and 0.42 eV (Sb). The barrier heights tend to track the band gap increase as the temperature is lowered. Forward I-V characteristics of the GaSb Schottky diodes at 300 K have ideality factors in the range 1.9–2.4, indicating that generation-recombination current from a near midgap center is dominating the behavior. At room temperature and below, the activation energy for Js in the expression J=Jsexp(qV/nkT) is 0.24 eV. However, at higher temperatures the activation energy becomes more nearly equal to the barrier height as deduced from C-V measurements and the n value decreases below two. Deep level transient spectroscopy (DLTS) measurements reveal the presence of one electron trap with a concentration around 1015 cm−3 at 0.25 eV below the conduction band edge. Electron beam induced current (EBIC) measurements give an electron diffusion length of 1.3 μm. In GaSb p-n+ junctions grown by molecular beam epitaxy, DLTS measurements show the presence of a generation-recombination center at Ev+0.33 eV with a concentration of 5×1014 cm−3. The effective lifetime inferred from the saturation current value is around 2×10−9 s. For reverse bias, the mechanism of breakdown at large voltages in p-n+ structures includes tunneling via local centers with an energy of around 0.3 eV. Forward and reverse characteristics can be improved by (NH4)2S treatments for both Schottky barriers and pn+ junctions.