Atomic scale analysis of the effect of the SiO2 passivation treatment on InAs/GaSb superlattice mesa sidewall

Abstract

We have analyzed by electron microscopy techniques the effect of the deposition of a SiO2 passivation layer on an InAs/GaSb type-II superlattice (SL) mesa with applications as a photodetector. Our images reveal good conformal coverage by the SiO2 upon an undulating edge of the SL mesa. However, we have observed scarce As clusters at the interface between the SL mesa and the passivation layer and some degree of oxidation of the mesa sidewall. The strong reduction in surface leakage currents demonstrates that the observed imperfections do not have a substantial detrimental effect on the passivation capabilities of the SiO2 layer.

Passivation of type II InAs/GaSb superlattice photodetectors with atomic layer deposited Al<sub>2</sub>O<sub>3</sub>

“…The peak D*, was equal to 1.9 x 10 13 Jones for the Al 2 O 3 passivated single pixel photodetector at 4 µm and 77 K. Under single pass front illumination conditions quantum efficiency (QE) of the passivated photodetector was determined as % 41. A comparison of our results with recent data [9,[16][17][18][19][20], shows that ALD grown Al 2 O 3 passivated T2SL photodetectors are very promising. Oxide layers of few nanometers thick native oxide layers form very quickly on freshly etched surface of the superlattice since they are very reactive [21].…”

“…Figure 2a Our electrical measurements showed that Al 2 O 3 is a better alternative for SiO x passivation. The significant reduction in dark current and increase in dynamic resistance due to ALD deposited Al 2 O 3 passivation is very encouraging for use in FPA applications [9,16,17]. The inverse of the dynamic resistance area product at zero bias as a function of the perimeter to area ratio at 77K for passivated and unpassivated detectors are shown in Fig.…”

Characterization of LWIR diodes on InAs/GaSb Type-II superlattice material

“…5 shows the SiO 2 /SLS interface on an atomic scale [6]. One can see the orderly arrangement of the columns of atoms in the SLS material in contrast with the amorphous nature of the SiO 2 .…”

“…Fig. 1 shows a cross-section of a mesa and the adjacent trench [6]. The superlattice material is 2.28 lm thick and rests upon the GaSb buffer layer.…”

“…At the highest spatial resolution the compositional analyses were performed also by means of electron energy loss spectroscopy (EELS). The TEM investigations were carried out under the direction of N.D. Browning of the University of California at Davis, and additional details have been reported elsewhere [6].…”