InAs/GaSb superlattice (SL) is a peculiar quantum system for infrared detection, where electrical and optical
properties are directly governed by the composition and the periodicity of the InAs/GaSb cell. Indeed, several
structures with different InAs to GaSb thickness ratios in each SL period, can target the same cut-off wavelength.
Likewise, the type of conductivity of the non-intentionally doped SL structure is also linked to the InAs/GaSb
SL period. The objective of this communication is to use the flexibility properties of InAs/GaSb SL to design
and then to fabricate by MBE a pin photodiode where the active zone is made of different SL periods. Electrical
and electro-optical characterizations are reported. The results show that SL structure for the MWIR domain can
be designed by combining the best of each SL periods.
In this communication, we examine the influence of the SL period of InAs/GaSb superlattice (SL), with diverse InAs to
GaSb thickness ratio, on the material and device properties of midwave infrared pin photodiodes. Three SL devices made
of three different periods, but exhibiting the same cut-off wavelength at 5 μm at 77K, were grown by molecular beam
epitaxy on p-type GaSb substrates. Optical and electrical characterizations (photoluminescence, current-voltage,
capacitance-voltage, and photoresponse measurements) were performed and analyzed in order to explain the results
obtained. Our investigations show the strong influence of the SL composition on both the material and photodetector
properties, such as residual doping concentration, shape of the response spectra and dark current values.