Optical studies of molecular beam epitaxy grown GaAsSbN∕GaAs single quantum well structures

Abstract

In this work, the authors present a systematic study on the variation of the structural and the optical properties of GaAsSbN / GaAs single quantum wells ͑SQWs͒ as a function of nitrogen concentration. These SQW layers were grown by the solid source molecular beam epitaxial technique. A maximum reduction of 328 meV in the photoluminescence ͑PL͒ peak energy of GaAsSbN was observed with respect to the reference GaAsSb QW. 8 K and RT PL peak energies of 0.774 eV ͑FWHM of ϳ25 meV͒ and 0.729 eV ͑FWHM of ϳ67 meV͒ ͑FWHM denotes full width at half maximum͒ corresponding to the emission wavelengths of 1.6 and 1.7 m, respectively, have been achieved for a GaAsSbN SQW of N ϳ 1.4%. The pronounced S-curve behavior of the PL spectra at low temperatures is a signature of exciton localization, which is found to decrease from 16 to 9 meV with increasing N concentration of 0.9%-2.5%. The diamagnetic shift of 13 meV observed in the magnetophotoluminescence spectra of the nitride sample with N ϳ 1.4% is smaller in comparison to the value of 28 meV in the non-nitride sample, indicative of an enhancement in the electron effective mass in the nitride QWs. Electron effective mass of 0.065m o has been estimated for a SQW with N ϳ 1.4% using the band anticrossing model.

Nitrogen incorporation and optical studies of GaAsSbN∕GaAs single quantum well heterostructures

“…21 RT emission of 1.53 m with a FWHM of 45 meV has also been achieved on another in situ annealed SQW sample. These values are comparable to the best reported RT emission "near" 1.5 m of 35 meV at 1.48 m ͑Refs.…”

“…The latter tends to saturate for N ജ 0.9% as discussed later, which partly accounts for the observed small rate of reduction in the PL peak energy. We have achieved a band gap reduction of ϳ328 meV for N ϳ 1.4% and Sb ϳ 30% with respect to the GaAsSb ͑30% Sb͒, 21 while other groups observed a reduction of ϳ230 meV for N ϳ 1.2% and Sbϳ 26%, 6 ϳ196 meV for N ϳ 1.5% and Sbϳ 30%, 15 ϳ155 meV for N ϳ 1%, 3 and ϳ85 meV for N ϳ 0.7% and Sbϳ 15%, 8 with respect to their reference GaAsSb QW. Further, the energy reduction in our work is also relatively higher than those observed in the other dilute nitride systems, namely, GaAsN: 290 meV for ϳ1.6% N, 6 250 meV for N ϳ 1%…”

Structures based on GaAs(Sb)(N) semiconductor alloys for high efficiency multi-junction solar cells

“…An exponential-like tail at low energies of the band-to-band PL peak is also usually observed in Ga 1-x In x As 1-y N y [159][160][161]163,166,[169][170][171], GaAs 1-y N y [164][165][166] and GaAs 1-x-y Sb x N y [167,168], given to the PL peak an asymmetric lineshape. This tail is attributed to a localization effect attributed mainly to random fluctuations of alloy compositions [161,166,170,171].…”

“…These phenomena are proportional to the N concentration. The redshift observed is related to the amount of N in the alloy, accounting for the large bowing parameter at low concentration [159,168]. On the other hand, the considerable local strain introduced by the small N atoms make the crystallinity of the material worse [159].…”

“…All these effects have a significant influence in the PL spectra. In Ga 1-x In x As 1-y N y [159][160][161][162][163], GaAs 1-y N y [164][165][166] and GaAs 1-x-y Sb x N y [167,168] dilute nitrides, the band-to-band PL energy peak redshifts when N is introduced in the material, at the same time than the PL intensity rapidly decreases and the FWHM increases. These phenomena are proportional to the N concentration.…”