Incorporation of nitrogen in nitride-arsenides: Origin of improved luminescence efficiency after anneal

Abstract

A key to the utilization of nitride-arsenides for long wavelength optoelectronic devices is obtaining low defect materials with long nonradiative lifetimes. Currently, these materials must be annealed to obtain device quality material. The likely defect responsible for the low luminescence efficiency is associated with excess nitrogen. Photoluminescence and capacitance–voltage measurements indicate the presence of a trap associated with excess nitrogen which decreases in concentration upon anneal. Our films are grown by elemental source molecular beam epitaxy and the background impurity concentration is low, thus we have investigated the role of crystalline defects. High resolution x-ray diffraction showed improved crystal quality after anneal. We observed that the lattice parameter does not decrease linearly with nitrogen concentration for levels of nitrogen above 2.9 mol % GaN. The fact that Vegard’s law is not observed, despite theoretical calculations that it should, indicates that nitrogen incorporates in locations other than the group V lattice sites. X-ray photoelectron spectroscopy revealed that nitrogen exists in two bonding configurations in not-annealed material: a Ga–N bond and another nitrogen complex in which N is less strongly bonded to gallium atoms. Annealing removes this second nitrogen complex. A combined nuclear reaction analysis and channeling technique showed that not annealed GaNAs contains a significant concentration of interstitial nitrogen that disappears upon anneal. We believe that this interstitial nitrogen is responsible for the deviation from Vegard’s law and the low luminescence efficiency of not annealed GaNAs and GaInNAs quantum wells.

Effect of temperature on the optical properties of GaAsSbN/GaAs single quantum wells grown by molecular-beam epitaxy

“…Although the origin of these centers is not clearly understood at present, they might have several origins including the presence of extrinsic defects like impurity inclusions related to N incorporation. 44,45 Therefore, the model which holds that the quenching arises from defect or impurity centers induced by the presence of nitrogen, is consistent with the data and it is probably correct.…”

Effect of rapid thermal annealing: red and blue shift in photoluminescence of GaNAs grown by RF plasma-assisted molecular beam epitaxy

“…This is shown by an intermediate redshift in the PL peak energy in annealing temperature range lower than the optimum temperature. Furthermore, such changes were not accompanied by a shift towards higher Bragg angle for the GaNAs peak in HRXRD, a result different from others [6,7].…”

“…However, along with large improvement in the PL efficiency, a significant blueshift (9-50meV) of the maximum PL intensity position was also observed which seemed independent of the N composition. This blueshift effect in the PL peak energy has been attributed mainly to two possible reasons; (i) nitrogen out-diffusion from bulk GaNAs [3], and (ii) interdiffusion of N-As atoms near the interface of GaNAs/GaAs [4,5]. However, the results from our experiments suggest the presence of a different mechanism of diffusion.…”

“…al. [7], nitrogen can exist in two configurations in the GaNAs layer grown using a RF plasma nitrogen source; (i) by forming a covalent Ga-N bond (a substitutional 0 site: replacing As host sublattices with N atoms), an effect which primarily contributes to the band gap narrowing (redshift) due to the highly localized nature of the perturbation introduced by nitrogen atoms [8], (ii) by forming a nitrogen complex in which nitrogen is less strongly bonded to Ga atoms (an interstitial site).…”

Structural properties of GaAsN∕GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunneling microscopy

“…Nevertheless, the optical emission of ͑In͒GaAsN / GaAs quantum wells ͑QWs͒ showed typically a strong degradation when the N content is increased. [1][2][3] This has been frequently attributed to different phenomena, such as N being incorporated in interstitial positions, 4,5 compositional fluctuations in the alloy, [6][7][8] or a rough top interface. 8 All these have motivated a strong effort in the last years on the structural characterization of ͑In͒GaAsN alloys, but only very few of these studies were performed using cross-sectional scanning tunneling microscopy ͑X-STM͒.…”