Reaching detection wavelength shorter than 2μm by using type II InAs/GaSb superlattice structure

Type II InAs/GaSb superlattice (SL) structure has many advantages for infrared photodetector applications and its detection wavelength is proved to be able to cover the range of about 3 to 30 μm by tuning the constituent layer thickness and the thickness ratio of InAs to GaSb. However, it is important to explore the possibility to further extend the detection wavelength as far as possible to reach the short wavelength (SW) range or even shorter than 2 μm by using type II InAs/GaSb SLs.

We reveal that a strong In intermixing occurs during the growth of SW InAs/GaSb SL structure. The In intermixing is strongly related to the growth temperature and can have a very big impact on the SL band structure and is the reason why a detection wavelength smaller than 3 μm can`t be realized for a SL structure like InAs (3 ML)/GaSb (3 ML). To reduce the influence of the In intermixing on the SL band structure, besides lowering the growth temperature, another effective scheme is to increase the GaSb layer thickness in the SL structure. Experimentally, we find that the PL peak of an InAs (8 Å)/GaSb (21 Å) SL structure grown at 380 °C reaches 2.7 μm at 77 K. By using this SL structure, the 50% cutoff wavelength of a p-i-n type of detector reaches 2.56 μm at 77 K. We also demonstrate that type II InAs/GaSb SLstructure can reach the detection wavelength shorter than 2 μm by inserting thin AlSb barriers and the detector exhibits a narrow-band photoresponse feature (δλ/λ=10.3%).