The thermal annealing of nitrogen related traps in p-type InGaAsN and GaAsN is investigated by deep level transient spectroscopy (DLTS). Upon annealing, an apparent recovery of the photovoltaic properties correlates with changes in the DLTS data observed for InGaAsN and GaAsN diodes and solar cells, revealing that a nitrogen related E1 (EC−0.20eV) center has an important role in governing the solar cell performance. The large electron capture cross section (∼8.9×10−15cm2) of this center indicates that this defect may act as an efficient recombination center. Therefore, its complete removal by annealing or by some other process is essential for the high performance of GaInAsN solar cells. The internal quantum efficiency data were modeled to quantify the change in material properties associated with this improvement upon annealing. Annealed cells with indium impurity (InGaAsN) show a slightly higher photoresponse, which could be due to low scattering caused by In–N pair formation after annealing.

We have envisaged and designed a novel III-V nitride based deep ultraviolet light emitting diode (LED) with reasonably high efficiency at higher current density using a double-side grading in electron blocking layer (EBL). Double-side step-and linear-grading in EBL yield better performance attributable to improved hole injection, stifled electron overflow and diminished electrostatic field in the active region. The performance curves indicate that double sided linear grading in EBL has 5.63 times enhancement in power compared to the conventional LED and the efficiency droop is as low as 15% at the current density of 200 A cm −2 for the emission wavelength of ∼273 nm.

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