Optical properties of GaAs1−xNxalloys grown by molecular beam epitaxy (original) (raw)
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Journal of Applied Physics, 1985
Low-temperature photoluminescence (PL) measurements have been performed on several molecular-beam epitaxial high-quality GaAs layers showing varied electrical characteristics (nominally undoped and intentionally doped n or p type). This work is carried out with a view to investigate the influence of the centers responsible for the defect–bound-exciton emissions (d,x) on the electrical properties of the layers. After a systematic study of
Growth and Characterization of GaAs1-xNx Epitaxial Layers
2008
Metal-orqanik gaz faza epitaksial (MOGFE) üsulu ilə GaAs və Ge altlıqları üzərində yetişdirilmiş GaAs 1-x N x epitaksial təbəqələrinin Raman və Fotolüminescent xasələri tədqiq olunmuşdur. Horizontal reaktorlu qurğuda Trimetilgallium, Arsin və Dimetilhidrazin element mənbəyi kimi istifadə olunmuşdur. Nümunələr atmosfer təzyiqində, 500 0 C temperaturda DMHy və başqa element mənbələrindən gələn gaz axınlarınin nisbətinin dəyişdirilməsi ilə yaranan müxtəlif şəraitlərdə yetişdirilmişdir. Aşqarlanmış GaAsN-də azot (N) Raman spectrində 470 cm-1 oblastda lokal vibrasiya modlarının müşahidə olunması ilə aşkarlanır. 500 və 600 cm-1 arasında müşahidə olunan TO və LO kimi zəif Raman modları xəlitənin qaydasızlığı haqqında məlumat verir. Yetişdirilmiş nümunələrin fotolüminessensiya (FL) xassələri də tədqiq olunmuşdur. GaAs 1-x N x-in tərkibində azotun (x) konsentrasiyası təxminən 2.1% təşkil etdikdə, ond 77K temperaturda fotolumüminessensiya piki 1.15 eV-da müşahidə olunur. Исследованы Рамановские и люминесцентные свойства GaAs 1-x N x эпитаксиальных слоев выращенных на подложках GaAs и Ge методом металлоорганического химического газового осаждения (МОХГО). Триметильгаллий (ТМГ), Арсин (AsH 3) и диметильгидразин (DMHy) использовалась в качестве источников в установке с горизонтальным реактором. Образцы выращивались в атмосферном давлении при 500 0 C в разных режимах с изменением соотношения газовых поток DMHy и других элементых источников. Азот в легированном GaAsN обнаружен с помошью Рамановского спектра с наблюдением локальных вибриационных мод в области 470 cm-1. Слабые рамановские особенности второго порядка как ТО и LO пики наблюдаемые между 500 и 600 cm-1 , предупреждают о степени безпорядочности сплава. Фотолюминесцентные (ФЛ) свойства выращенных образцов также исследованы. Когда концентрация азота (х) внутри GaAs 1-x N x составляет приблизительно 2.1 %, то при температуре 77К фотолюминесцентный пик наблюдается при 1.15 эВ. Raman scattering and photoluminescence properties of GaAs 1-x N x epitaxial layers grown on GaAs and Ge substrates by means of metalorganic vapor phase epitaxy (MOVPE) have been investigated. Trimethylgallium (TMG), AsH 3 and Dimethylhydrazine (DMHy) were used as precursors in the setup with horizontal reactor. The samples were grown at atmospheric pressure at temperature 500 0 C and varying the molar ratio between DMHy and the other precursors. Nitrogen in diluted GaAsN has been detected by Raman scattering through the observation of the nitrogen local vibrational mode at about 470 cm-1. Weak GaAs second order Raman features like TO and LO peaks are observed between 500 and 600 cm-1 , evidencing alloy disorder. The photoluminescence (PL) properties have also been investigated on as grown samples. The PL peak energy of a GaAs 1-x N x is 1.15 eV at 77 K, when the N content (x) is about 2.1 %.
Physical Review B, 2006
Using microphotoluminescence ͑-PL͒, in dilute N GaAs 1−x N x alloys, we observe a PL band far above the bandgap E 0 with its peak energy following the so-called E + transition, but with contribution from perturbed GaAs host states in a broad spectral range ͑Ͼ100 meV͒. This finding is in sharp contrast to the general understanding that E + is associated with a well-defined conduction band level ͑either L 1c or N x ͒. Beyond this insight regarding the strong perturbation of the GaAs band structure caused by N incorporation, we demonstrate that a small amount of isoelectronic doping in conjunction with-PL allows direct observation of above-bandgap transitions that are not usually accessible by PL.
Compositional disorder in GaAs1−xNx:H investigated by photoluminescence
Physical Review B, 2006
Compositional disorder is investigated by means of photoluminescence ͑PL͒ and PL excitation ͑PLE͒ measurements in as-grown and hydrogen-irradiated GaAs 1−x N x samples ͑x ഛ 0.21% ͒. The dependence of the linewidth of the PLE free-exciton band on N concentration agrees well with that predicted by a theoretical model developed for a purely random alloy. We also find that hydrogen irradiation and ensuing nitrogen passivation reduce significantly the broadening of the free-exciton band. This result is consistent with a removal by hydrogen of the static disorder caused by nitrogen. Finally, an analysis of the dependence of the Stokes shift on the free-exciton linewidth shows that free carriers are thermalized even at low temperature, another indication of a low degree of disorder in the investigated samples.
MRS Proceedings, 1991
ABSTRACTWe report a cathodoluminescence (CL) and photoluminescence (PL) study of molecular beam epitaxy grown GaAs at low substrate temperatures (LT GaAs), and semi-insulating LEC GaAs. The as grown LT GaAs material shows intense deep level emissions which can be associated with an excess concentration of Arsenic. These emissions subside with annealing for a few minutes at temperatures above 450 ° C. CL measurements clearly show an extremelly reduced concentration of traps in the post-growth 600 ° C annealed material. These results account for a diminished role of electronic point defects in controlling the insulative behavior of LT GaAs and strongly support the “buried” Schottky barrier model.
Physical Review Materials, 2019
Although several approaches have been used in the past to investigate the impact of nitrogen (N) on the electronic structure of GaAs1−xNx alloys, there is no agreement between theory and experiments about the importance of the different N interstitial defects in these alloys, and their nature is still unknown. Here we analyze the impact of five different N defects on the electronic structure of GaAs1−xNx alloys, using density-functional methods: we calculate electronic states, formation energies and charge transition levels. The studied defects include NAs, AsGa, AsGa-NAs substitutional defects, and (N-N)As, (N-As)As split-interstitial complex defects. Our calculated defect formation energies agree with those reported by S.B. Zhang et al. [Phys. Rev. Lett. 86, 1789 (2001)], who predicted these defects. Among the interstitial defects, we found that (N-As)As emerges as the lowest energy configuration in comparison with (N-N)As, in agreement with recent experiments [T. Jen, et al., Appl. Phys. Lett. 107, 221904 (2015)]. We also calculated the levels induced in the electronic structure due to each of these defects: defect states may occur as deep levels in the gap, shallow levels close to the band edges, and as levels resonant with bulk states. We find that the largest changes in the band structure are produced by an isolated N atom in GaAs, which is resonant with the conduction band, exhibiting a strong hybridization between N and GaAs states. Deeper levels in the bandgap are obtained with (N-N)As split-interstitial defects. Our results confirm the formation of highly localized states around the N sites, which is convenient for photovoltaics and photoluminescence applications.
Superlattices and Microstructures 65 (2014) 48–55.
The effects of long time thermal annealing at 200 C on the optical and structural properties of GaAs1xBix alloys were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). FESEM images show that bismuth islands nucleate on the surface and their diameter increases after annealing. It was observed a PL intensity enhancement and a small blue shift in PL peak energy after thermal annealing at 200 C for 3 h of GaAs1xBix alloys which was associated to the reduction of the density of defects. However these defects are not completed removed by thermal annealing although an important PL intensity improvement is observed.
Current Applied Physics, 2015
This work reports the effect of gamma (g-) irradiation on dilute GaAsN with nitrogen concentrations ranging from 0.2 to 1.2% with post-irradiation stability using CurrenteVoltage (IeV) and Deep Level Transient Spectroscopy (DLTS) measurements in the temperature range from 10 K to 450 K. The IeV results indicate that the irradiation effect was more pronounced in the samples with nitrogen concentration of 0.4%. Additionally, the irradiated samples showed an ideality factor higher than the as-grown samples. On the other hand, for temperatures above 265 K the barrier height of the irradiated samples with 0.8% nitrogen is higher than the as-grown samples. The DLTS measurements revealed that after irradiation the number of traps either decreased remained constant, or new traps are created depending on the concentration of nitrogen. For samples with N ¼ 0.2% e 0.4% the number of traps after irradiation decreased, whereas for samples with N ¼ 0.8% À 1.2 % the number of traps remained the same. However, the properties of some traps such as capture cross-sections and density increased by about 2 orders of magnitude. The origin of the defects present before and after irradiation are discussed and correlated.