The photoluminescence of GaAs 0.973 Sb 0.022 N 0.005 was investigated at different temperatures, pressures, and excitation powers. Both the alloy band edge and the N-cluster emissions, which show different temperature and excitation power dependences, were observed. The pressure coefficients obtained in the pressure range of 0 -1.4 GPa for the band edge and N-related emissions are 67 and 45 meV/ GPa, respectively. The N-cluster emissions shift to higher energy in the lower pressure range and then begin to redshift at about 8.5 GPa. This redshift is possibly caused by the increase of the x-valley component in the N-related states with increasing pressure. A rapid decrease of the emission intensity of the N-related band was also observed when the pressure exceeded about 8 GPa.

A GaInP/Ga(In)As/GaNAsSb/Ge 4J solar cell grown using the combined MOVPE + MBE method is presented. This structure is used as a test bench to assess the effects caused by the integration of subcells and tunnel junctions into the full 4J structure. A significant degradation of the Ge bottom subcell emitter is observed during the growth of the GaNAsSb subcell, with a drop in the carrier collection efficiency at the high energy photon range that causes a~15% lower J sc and a V oc drop of~50 mV at 1-sun. The V oc of the GaNAsSb subcell is shown to drop by as much as~140 mV at 1-sun. No degradation in performance is observed in the tunnel junctions, and no further degradation is neither observed for the Ge subcell during the growth of the GaInP/Ga(In)As subcells. The hindered efficiency potential in this lattice-matched 4J architecture due to the degradation of the Ge and GaNAsSb subcells is discussed. At this stage of development, it is pertinent to have a closer look at the integration of components forming the 4J structure. For example, the insertion of the dilute nitride subcell in the 3J structure brings about added thermal loads to the Ge bottom subcell, an effect accentuated by the fact that dilute nitrides usually require an annealing step to improve their electronic properties. The dilute-nitride subcell itself suffers annealing during the growth of the upper subcells, which could be expected to have an impact on its performance. The focus has to be put in identifying and quantifying these effects, and redesigning the growth process to minimize their impact.In this work, we present a detailed characterization of our 4J solar cell, based on a prototype structure achieved by a combination of MOVPE + MBE growth methods, and using a GaNAsSb junction.This solar cell succeeds in integrating 4 component junctions into a monolithic, lattice matched structure, but it is still far from being a high efficiency device, mainly due to sub-optimum characteristics of the dilute nitride subcell. However, the device provides valuable insight into the integration of the dilute nitride subcell into a 4J solar cell. We focus mainly on the effect of thermal load on the performance of the Ge and GaNAsSb bottom subcells, and the tunnel junctions. It is found that significant losses are at stake, mainly in the Ge and GaNAsSb subcells, which can limit the potential of this 4J solar cell structure to compete in efficiency with other architectures.

The InSb photodetector on a Si substrate acts a signal receiver for the mid-infrared silicon photonics application to overcome the limitation of group IV semiconductors.In this paper, we demonstrated an InSb p-i-n photodetector with an InAlSb barrier layer grown on (100) silicon substrates via a GaAs/Ge buffer by molecular beam epitaxy. The lattice mismatch between InSb and GaAs was accommodated by an interfacial misfit (IMF) array. The 50% cutoff detectable wavelength of this detector increased from 5.7 µm at 80 K to 6.3 µm at 200 K. An 80 K detectivity of 8.8×10 9 cmHz 1/2 W -1 at 5.3 µm was achieved with a quantum efficiency of 16.3%. The dark current generating mechanism of this detector is both generation-recombination and surface leakage above 140 K, while it is only surface leakage from 120 K to 40 K.

The authors report on picosecond pulse response GaNAsSb∕GaAs p-i-n photodetectors grown by molecular beam epitaxy in conjunction with a rf plasma-assisted nitrogen source. The 2μm thick GaNAsSb photoabsorption layer contains 3.3% of N and 8% of Sb resulting in a dc photoresponse up to 1380nm wavelength. Dark current densities at 0 and −5V are 1.6×10−5 and 13A∕cm2, respectively. The GaNAsSb photodiodes exhibit a record pulse response width of only 40.5ps (full width at half maximum) corresponding to a 4.5GHz bandwidth.

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