Low-temperature emission in dilute GaAsN alloys grown by metalorganic vapor phase epitaxy

Abstract

We have investigated the optical emission from GaAs 1−x N x epilayers with 4.3ϫ 10 −4 Ͻ x Ͻ 0.012. The samples were grown on GaAs͑001͒ substrates by metal-organic vapor phase epitaxy using dimethylhydrazine as the nitrogen precursor. We find that the incorporation of nitrogen in GaAs generates deep radiative centers at around 250 meV below the GaAsN band gap. The defects associated with these centers can be eliminated through an optimization of the growth temperature and reactor pressure, and by postgrowth annealing at 700°C. We also find that, contrary to what was suggested by Makimoto et al. ͓Appl. Phys. Lett. 70, 2984 ͑1997͔͒, the near-gap emission located close to 25 meV below the gap is not related to a free-to-bound transition even in the samples with the lowest nitrogen content. Rather, we associate this emission to excitons bound to overlapping nitrogen clusters.

Tailoring the electrical conductivity of GaAs by nitrogen incorporation

“…This high concentration of traps indicates that the chemical potential is somewhere between the energy level of the localized states and the CB edge. Thus, for x > 0.2%, the binding energy E b of the electron trap is approximately equal or larger than E. This is consistent with the value of E b ∼ 0.25 eV extracted from recent PL studies of nominally undoped GaAs 1−x N x epilayers [24] and attributed to a complex involving a Ga-vacancy (V Ga ) and a N antisite (N Ga ) [25,26]. The concentration of these acceptor complexes increases with N content [24][25][26], in agreement with the strong reduction of the free electron density and PL intensity observed in our samples at x > 0.2% (figure 1(c)).…”

N incorporation and optical properties of GaAsN epilayers on (3 1 1)A/B GaAs substrates

“…According to reported influences of RTA on the PL efficiency of GaAsN layers grown by MBE, the minimum full width at half maximum (FWHM) and the highest integrated intensity of the PL peak occurred at annealing temperatures of ∼700-750 • C for samples with 1.3% and 2.2% N content [20]. The same annealing condition to our choice has also been shown to be effective in studying the optical behaviour related to DLs in GaAsN [13]. Figure 6 compares the LT-PL spectra measured before and after annealing.…”

“…A band-structure modification might occur at relatively high N composition on specific high-index orientations, but further experimental proofs are still needed to confirm it. Although direct evidence of the nature for DLs related to 1.1 eV emission is still unavailable, effects from the growth conditions and postgrowth annealing on both spectral shape and intensity were investigated [13,14]. Main features to the DL emission from available reports include the following: (1) the emission has no relationship to GaAs host materials; (2) for samples grown at the same temperature, high N composition results in a high relative intensity; (3) for samples with comparable N contents, high temperature tends to weaken the intensity; (4) postgrowth rapid thermal annealing (RTA) is effective to reduce the emission.…”

Extremely uniform bound exciton states in nitrogen δ-doped GaAs studied by photoluminescence spectroscopy in external magnetic fields

“…The optical and electronic properties of dilute nitride alloys are drastically modified by the interaction between the host-material conduction-band edge and nitrogen (N)-related defect levels. [1][2][3] In particular, the electronic states created by N substitution in Ga(In)As have been attracting considerable interest both from a fundamental perspective [4][5][6][7][8] and their potential device applications such as long-wavelength laser diodes, [9][10][11][12][13] low-noise avalanche photodetectors, 14 and multiband solar cells. 15 These important applications can be realized by using properties of the strongly localized states in the infrared region.…”