Customers’ demands of wider spectral band absorption detectors in MWIR/LWIR region with competitive parameters to MCT technology encouraged VIGO to develop a novel class of materials & detectors. InAs/InAsSb superlattice (SL) based detectors are our response to fully RoHS compliant product designed for operation with thermoelectric coolers (TEC) at HOT conditions.
NO LIQUID NITROGEN COOLING REQUIRED: LWIR immersed SL detectors work perfectly stable in difficult conditions and have higher normalized detectivity compared to PC and thermopile detectors.
FAST MULTIGAS ANALYZER WITH ONE IR DETECTOR: MWIR immersed SL detectors operate with no bias at a wider spectral range and are characterized by higher frequencies than PbSe detectors.
Currently manufactured widely used detectors are made with mercury-cadmium telluride compound (MCT) by Metalorganic Chemical Vapour Deposition (MOCVD) technology. Despite many advantages of MCT compound, nowadays in some applications, detectors containing mercury, cadmium and lead are successively removed from the consumer market through norms and directives (e.g. RoHS) due to their toxicity.
Abovementioned limitations connected to MCT encouraged the company to find alternative material system and technology. The InAsSb ternary III-V compound is a great candidate, operating in similar wavelength regime. Encouraged by literature and scientific partners, VIGO decided to develop Ga-free InAs/InAsSb superlattices.
After three years of work on MBE growth technology of InAs/InAsSb SL on SI GaAs substrates, VIGO is ready to present a first generation of SL products with parameters comparable to MCT. So far, we have successfully manufactured photovoltaic devices (MWIR) and photoconductive devices (LWIR).
MWIR SUPERLATTICE DETECTORS
For MWIR detection VIGO is developing SL detectors operating at room temperature or with the use of a two-stage thermoelectric cooler (at 230 K). Recent results showed that SL detectors exhibit higher resistance area (RA) product in comparison to bulk InAsSb devices. That allows us to produce wider spectral band detectors (Fig. 1) exhibiting satisfactory detectivity.
Advantages:
- Cut-on wavelength limited to transmission of GaSb buffer ~1.7 μm
- High RA product and D* to similar to MCT (Fig. 2)
- RoHS compliant product
- Wider spectral range and higher operating frequencies than PbSe detectors (quicker detection of many gases with one device )
- Operation without bias (elimination of 1/f noise present in photoconductors)
| Parameter | Detector type | |
| Photovoltaic | ||
| Active element material |
InAs/InAsSb backside illuminated |
|
| Active element temperature, K | 300 | 230 |
| TEC | Non-cooled | 2-stage |
| Peak wavelength, µm | 4.0 – 4.5 | |
| Spectral range, µm | 1.7 – 5.9 | 1.7 – 5.6 |
| λCutoff (10%), µm | ~6.0 | ~5.7 |
| D* (λpeak), cm·Hz1/2/W | >5 x 108 | >4 x 109 |
| Responsivity (λpeak), A/W | >0.7 | >1.4 |
| Shunt impedance (@VR =10 mV), Ω | >110 | >1000 |
| Active area dimensions, mm |
0.1 x 0.1 1 x 1 immersed |
|
| Package | TO-39 | TO-8 |
LWIR SUPERLATTICE DETECTORS
For LWIR detection VIGO is developing detectors both on 2 and 3 stage thermoelectric coolers (operating at 230 K and 210 K respectively). We are able to offer detectors optimized for 10 μm and 12 μm (possibility up to 15 µm and even more). Recent results showed that SL detectors exhibit sheet resistance comparable to MCT technology at 210-230 K temperature range. This is the first RoHS compliant product for LWIR detection that does not require liquid nitrogen cooling! This product line opens a new perspective for spectroscopy.
ADVANTAGES:
- Cut-on wavelength limited to transmission of GaSb buffer ~1.7 µm
- Higher D* compared to PC InAsSb and thermopile detectors
- RoHS compliant product
- Very good stability ideal for harsh environment
- 50% cut-off wavelength optimized for 10 or 12 μm
NO LIQUID NITROGEN COOLING REQUIRED! (Fig. 4)
| Parameter |
Detector type | |
| Immersed 3TE photoconductive | ||
| Active element material |
InAs/InAsSb backside illuminated |
|
| Active element temperature, K | 210 | |
| Peak wavelength, µm | 7.0 – 9.0 | |
| Spectral range, µm | 1.7 – 11.5 | |
| λCutoff (10%), µm | ~12 | |
| D*(λpeak), cm·Hz1/2/W (@0.5 V) | >3 x 109 | |
| Resistance , Ω | >60 | |
| Active optical area , mm | 1 x 1 | |
| Package (window) |
TO-8 (wZnSeAR) |
|