During the growth, all the InAs 0.9Sb 0.1 layers in the device structure was grown as InAs-InSb binary-binary digital alloy 22. The InAs 0.9Sb 0.1 bulk material was also used as the absorption layer for the mid-wavelength infrared detection at 150 K. The effective conduction band of the H-structure superlattice moves upward significantly due to the confinement of the electrons in the GaSb well by the AlAsSb barrier layers. The ETBM material parameter sets in the previous work were used 21. The bandgap energy of the H-structure superlattice was calculated to be around 1 eV at 150 K by the empirical tight-binding method (ETBM) with sps* formalism which was modified from previous work 20, 21. For convenience, ‘AlGaAsSb’ will be used to refer to the AlAsSb/GaSb H-structure superlattice in the rest of discussion. The AlGaAsSb barrier layer in the MQW structure was grown as an AlAs 0.1Sb 0.9/GaSb superlattice, This SLS is called an H-structure superlattice and can be used as an electron barrier layer in some type-II superlattice infrared photodetector designs 19. The MWIR SAM-APD device was grown by molecular beam epitaxy with the multiplication layer consisting of an AlGaAsSb/InAs 0.9Sb 0.1 MQW. The separate absorption layer used in the SAM-APD is an InAsSb alloy chosen to cover the mid-infrared range at an operating temperature of 150 K. Therefore, it is promising to use the MQW approach, with antimony-based SLS barriers, as the multiplication layer in the APDs. As demonstrated by McIntyre 18, a large difference in the ionization rates for electrons and holes is essential for a low noise avalanche photodiode.
![cut off wavelength definition for lionight absorpt cut off wavelength definition for lionight absorpt](https://www.rp-photonics.com/img/step_index_fiber_mode.png)
This MQW enables using the antimony-based SLS to engineer a large difference in the ionization rates for electrons and holes by designing the band discontinuities between well and barrier to have a large difference between conduction band offset ( ∆E c) and valence band offset ( ∆E v). The SAM structure can be used to reduce excess noise factor and also enhance the multiplication noise gain through impact-ionization engineering 16, 17.ĭue to the great band structure engineering flexibility, an antimonide-based SLS can be used as the barrier layer for a multi-quantum well (MQW) heterostructure when combined with an InAsSb well. However, their performance, especially the excess noise factor, is limited due to the relatively small difference in the ionization rates for electrons and holes or because both electrons and holes are injected into the multiplication region.
![cut off wavelength definition for lionight absorpt cut off wavelength definition for lionight absorpt](https://slideplayer.com/7568554/24/images/slide_1.jpg)
Recently, the MWIR APDs based on III–V superlattices have been demonstrated 15. The emerging material system, antimony-based strained layer superlattices (SLS) have drawn lots of attention due to the advantages of high material uniformity, great bandgap tunability and Auger recombination suppression compared with HgCdTe detectors 11, 12, 13, 14.
![cut off wavelength definition for lionight absorpt cut off wavelength definition for lionight absorpt](https://www.shimadzu.com/an/sites/shimadzu.com.an/files/d7/ckeditor/an/hplc/support/qn50420000002cjd-img/qn50420000006kmq.gif)
However, the HgCdTe-based APDs suffer from drawbacks such as material instability and low fabrication yields 9, 10.
![cut off wavelength definition for lionight absorpt cut off wavelength definition for lionight absorpt](https://www.researchgate.net/profile/Jill-Zamzow/publication/263135467/figure/fig1/AS:671517704716289@1537113705064/The-50-cutoff-wavelength-for-the-lens-and-whole-eyes-of-Dascyllus-albisella-as-a.png)
Compared with the HPTs, the APDs can amplify weak signals without the relatively more complicated HPT device structure 6.įor MWIR APD devices, HgCdTe is the state-of-art material system and has been widely used in infrared APDs 7, 8. Therefore, gain-based devices such as heterojunction phototransistors (HPTs) and avalanche photodiodes (APDs) are used to achieve the necessary photoresponse when the incoming photon flux is low 3, 4, 5. In most of these applications there is a need to increase the capability of the system to detect light in a low photon flux situation. Mid-wavelength infrared (MWIR) photodetectors which can operate under the low flux conditions are of great interest for long-range military and astronomical applications 1, 2.