The subband features E‒ and E+ for the conduction band of III-V dilute nitride alloys make them promising for intermediate band solar cell application. However, presence of bandgap states can limit the two-step photon absorption activity, a necessary requirement for IBSC functionality. A model analysis is performed to characterize the density of states. The sub-band tails states are characterized using a temperature-dependent map of photo-modulated reflectance spectroscopy for GaNAs thin films grown on GaAs substrates using molecular beam epitaxy. The effect of indium and antimony incorporation on the subband features were investigated. Marked improvements in the thin films were observed both for the lower (E‒) and the upper (E+) conduction bands (CB) when In was introduced with marginal enhancement by Sb. These improvements are associated with suppression of tail states below both the E‒ and E+ bands. Sb rather mainly plays a surfactant role improving the abruptness of the GaNAs/GaAs hetero-interface.
Nazmul Ahsan, Naoya Miyashita, Kin Man Yu, Wladek Walukiewicz, and Yoshitaka Okada, "Multiband modification of III-V dilute nitrides for IBSC application," Proc. SPIE 10099, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI, 100990I (Presented at SPIE OPTO: January 31, 2017; Published: 29 March 2017); https://doi.org/10.1117/12.2250700.
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