Effect of SU-8 Passivation Layer Induced Stress on the Performance of GaSb Diode

SU-8 was found to be a good candidate for passivation of GaSb diodes, because of its stable chemical properties and high resistivity. However, stresses might be induced during the SU-8 solidification process, which could affect the performance of GaSb diode. Here, we measured the dark currents of devices with different sizes of mesa area and thicknesses of passivation layer, found that the thickness of passivation layer is a key factor for the performance of GaSb based devices. The dark current density of the optimum passivated diode is 9.80 x 10-6 A/cm 2 (at -0.3 V bias) and the calculated surface resistivity based on dynamic resistance-area product (R0A) of the passivated diode is 854 Ω · cm, which are about twentyfold decrease and sixfold increase than that for unpassivated diodes at 77 K, respectively. The calculated quantum efficiency is 36.3% for the passivated device, whereas the value for the unpassivated device is 19.2%.