Band Gap Reduction in InAsN Alloys

Abstract

We report the structural, electrical and optical properties of bulk InAsN alloy with various nitrogen contents deposited on (100) InP substrates using plasma-assisted gas-source molecular beam epitaxy. From absorption measurements, it is found that the fundamental absorption energy of InAsN is higher than that of InAs due to the Burstein-Moss effect resulting from the high residual carrier concentration in InAsN. To deduce the 'real' band-gap energy of InAsN samples, the energy shift due to the Burstein-Moss effect and the band-gap narrowing effect are calculated by using a self-consistent approach based on the band-anticrossing (BAC) model [Shan et al.: Phys. Rev. Lett. 82 (1999) 1221. After correction, the 'real' band-gap energy of InAsN samples decreases as N increases. The electron effective mass of InAsN is also investigated by plasma-edge measurement. We found a sizeable increase of the electron effective mass in these InAsN alloys, which is consistent with the theoretical predictions based on the BAC model.

Photoluminescence spectroscopy of bandgap reduction in dilute InNAs alloys

“…A value of 1.48 eV was used, in agreement with that obtained by Shih et al 7 Using the BAC model, 1 the experimental data are reproduced when the nitrogen level and coupling parameter have the values E N 0 = 1.48 eV ͑with ␥ = 2.00 eV͒ and C MN = 1.77 eV, respectively. This value of C MN is between those of 1.68 and 1.86 eV reported by Shih et al 7 and Kuroda et al, 8 respectively, obtained from fitting the N content dependence of the absorption edge after correcting for Moss-Burstein shift.…”

“…8 Therefore, the nitrogen-induced band gap reduction in InNAs can generally only be estimated from absorption spectroscopy once the contribution of Moss-Burstein shift to the position of the absorption edge has been modeled. [7][8][9] In this letter, the temperature dependence of photoluminescence ͑PL͒ from dilute InNAs films grown by MBE is reported. The PL spectra unambiguously show band gap reduction with increasing N content.…”

“…3,4 While a great deal of attention has been paid to GaNAs and GaInNAs alloys for nearinfrared applications, the investigation of related dilute nitride alloys, such as GaNSb ͑Ref. 5͒ and InNAs, [6][7][8][9] for midinfrared applications is only in its infancy. Indeed, band gap reduction has proved difficult to observe unambiguously in absorption spectra from InNAs alloys.…”

“…Indeed, band gap reduction has proved difficult to observe unambiguously in absorption spectra from InNAs alloys. [7][8][9] The reduction of the absorption-edge energy with increasing nitrogen content has so far only been observed in one optical absorption study of InNAs alloys. 6 Generally, absorption edges at higher energies than the true band gap are observed in n-type InNAs epilayers.…”

“…6 Generally, absorption edges at higher energies than the true band gap are observed in n-type InNAs epilayers. [7][8][9] This is due to the Moss-Burstein effect, 10,11 resulting from band filling due to unintentionally degenerate n-type doping in the InNAs alloy. This proclivity of InAs and InNAs for n-type conductivity is consistent with the amphoteric defect model.…”