| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
R1, Improved Performance of Long-Wave Infrared InAs/GaSb Strained Layer Superlattices Detectors by Novel ZnTe Passivation |
| Author(s) |
Maya Narayanan Kutty, Elena Plis, Svyatoslav Smolev, Nutan Gautam, Mikhail Naydenkov, Stephen Myers, Ralph Dawson, Weiming Wang, Jamie Phillips, Sanjay Krishna |
| On-Site Speaker (Planned) |
Maya Narayanan Kutty |
| Abstract Scope |
Present-day fabrication of SLS based detectors involves termination of periodic crystal structure while performing individual pixel isolation (Mesa structures). Amid this process, unsatisfied (dangling) chemical bonds are formed on the exposed sidewalls responsible for generation of surface states within the bandgap and enhanced leakage currents. In order to overcome the limitation imposed by surface leakage currents, a stable surface passivation layer is needed. However, passivation treatment applied on rough surfaces, or surfaces contaminated by native oxides or foreign particles will result in little or no improvement of device performance. Definition of mesa sidewalls that are free of native oxide and defects is the crucial step in InAs/GaSb SLS FPA fabrication process.
We have previously found that the smoothest sidewall profile of large-area (400μm x 400μm) LWIR (λ50% cut-off ~ 14μm) InAs/GaSb SLS detectors was obtained after chemical HCl-based etch (H2O2 : HCl : H2O = 1 : 1 : 4) while the plasma-assisted etch performed on the same material, generated a lot of damage, in particular, etch residues and two-step sidewall profile was observed. However, the same chemical etch utilized for the isolation of 24μm x 24μm mesas (the FPA pixels) resulted in significant lateral etch (~9μm each side) and rough sidewall. Plasma-assisted (ICP) etch resulted in smooth vertical sidewalls of individual FPA pixels free from any etch residuals with no undercut (with respect to mask) observed as well as clean FPA grooves. However, it’s known that plasma-assisted etch produces inevitable degradation of sidewall surface electronic properties due to ion bombardment or unwanted deposition of etch by-products. We tried to partially restore damage produced during the dry etch may be subsequent chemical treatment with HCl-based etch. The application of chemical etch subsequent to the plasma-assisted etch resulted in undercut estimated to ~ 8μm on each side of FPA mesa. Thus, the final size of defined mesa is only 8μm x 8μm, which is not acceptable for the subsequent FPA fabrication steps. To compensate the surface damage induced by ICP etch and further reduce the surface leakage currents, passivation needs to be applied on the etched sidewalls. Chalcogenide passivation such as ZnS or ZnTe successfully saturates dangling bonds and reduces the possibility of native oxide (such as Ga2O3, SbO2) formation. We found that quality of ZnS is poor, probably, due to the deposition process (e-beam dielectric evaporation). We developed ZnTe passivation as an alternative to the ZnS, and we expect to achieve the better passivation quality since ZnTe is deposited through the molecular-beam epitaxy (MBE) technique. During the presentation the etch study results for InAs/GaSb LWIR SLS FPAs will be presented along with the novel ZnTe passivation device results. |
| Proceedings Inclusion? |
Undecided |