Influence of heterovalent doping on tetrahedral N interstitial formation in dilute GaAsN alloys

Abstract

Dilute alloying of GaAs with N enables bandgap tuning for near-infrared to mid-infrared optoelectronic devices. However, non-substitutional N incorporation has been linked to lower absorption and emission efficiencies in dilute-nitride-alloy-based devices, especially in those containing heterovalent dopants. In this work, we examine the influence of heterovalent dopants on N incorporation mechanisms in dilute GaAs1−xNx alloys with N composition intentionally below the threshold composition for the formation of tetrahedral N interstitials (Ntetra) in undoped GaAs1−xNx. For undoped GaAs1−xNx, 20% of the N incorporates in non-substitutional sites, as (N-N)As and (N-As)As split interstitials. Interestingly, Si dopants induce the formation of Ntetra, while Be doping has a negligible effect on the interstitial type. Although elastic interactions due to opposite signs of the misfit volumes of Ntetra and NAs contribute to Ntetra incorporation above a threshold N composition, Si dopants reduce the threshold composition, due to the Fermi level-dependent stability of Ntetra.