Electronic structure of functional region of the interband cascade infrared photodetector designed to operate with cut-off wavelength of ~10.7 μm is calculated using second nearest neighbor sp3s* tight binding model with spin-orbit interactions. The effective bandgaps and alignment of the band edges are presented. Lattice mismatch of each region to the GaSb substrate is determined. The influence of InAs incorporation into the InSb interfacial layer is investigated. It is shown that up to 5% InAs addition to InSb interface in InAs/GaSb superlattice absorber is allowed if efficient carrier transport is to be kept. Furthermore, interface of up to x=2% InAsxSb1-x can be used in the proposed InAs/AlSb superlattice intraband relaxation region to keep its proper operation.
Measurements of low-frequency noise of type-II superlattice detectors designed for mid-IR wavelengths are used to determine noise limitations, calculate the real detectivity, and study 1/f noise-current correlations in these devices. No 1/f noise connected to the diffusion current is found as opposed to the generation-recombination, shunt, and tunneling currents. The contribution from the shunt current to 1/f noise can be so large that shunt-originated noise dominates in the high-temperature region, in which current is limited by the generation-recombination and diffusion components. It is also demonstrated that devices made of type-II superlattice contain traps generating random processes with thermally activated kinetics, and the activation energies of these traps are determined.
For the growth of many high-quality photonic devices, especially surface emission lasers with a vertical resonance
cavity (Vertical External Cavity Surface Emitting Laser, VECSEL) very important is to know the actual concentration of
the carriers in each layer laser structure resulting from the presence of unintentional impurities. Studies of doping profile
of this type multilayer structure can be carried out only by comparing the measured capacitance - voltage characteristics
with the calculated theoretically. The paper presents results of research VECSEL structures with different numbers of
quantum wells 4, 8, 12, 16, produced by molecular beam epitaxy. Measurements of the capacitance - voltage
characteristics has been performed using mercury probe in the system for automatic measurement of C-V, I-V, G–V. The
results of C-V measurements and numerical simulations have confirmed the possibility to control the level of
unintentional impurities in the different layers of the laser VECSEL structure. The lowest concentrations of unintentional
impurities were obtained for structures with highest power output.
Using a Vertical Cavity Surface Emitting Laser (VECSEL) “as-grown” heterostructure we set-up a laser emitting at 488
nm with the output power approaching 20mW. The short wavelength emission was due to the conversion of the 976nm
emission by a second harmonic generation process in a type-I lithum triborate (LBO). The V-type external cavity
permitted efficient focusing of the laser beam on both the VECSEL heterostructure and the non linear crystal. A small
diameter focused spot on the gain mirror is required when “as-grown” heterostructures are used. No birefringent filter
was used in the resonator. In the case of our heterostructure we observed that the light was spontaneously polarized
along the one of the crystallographic direction. The polarization ratio was 1000:1. The VECSEL heterostructure was of
the resonant type strongly enhancing a single wavelength emission. The wavelength fine tuning was performed by
heatsink temperature adjustment. The heterostructure was grown by molecular beam epitaxy. It consisted of 12 InGaAs
quantum wells enclosed by GaAs barriers and a AlAs/GaAs DBR.