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GaN/AlN short-period superlattices for intersubband optoelectronics: A systematic study of their epitaxial growth, design, and performance
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10.1063/1.3003507
/content/aip/journal/jap/104/9/10.1063/1.3003507
http://aip.metastore.ingenta.com/content/aip/journal/jap/104/9/10.1063/1.3003507

Figures

Image of FIG. 1.
FIG. 1.

Variation in the surface morphology of GaN/AlN MQW structures as a function of the Ga coverage during growth.

Image of FIG. 2.
FIG. 2.

AFM images of samples grown by different methods: (a) E617 grown with In as a surfactant, (b) E609 grown with Ga excess, and (c) E610 grown using Ga and Al excess and with growth interruptions.

Image of FIG. 3.
FIG. 3.

HRTEM images of GaN/AlN MQW structures grown using the IS, GS, and GI techniques, respectively.

Image of FIG. 4.
FIG. 4.

HRXRD scan of the (0002) reflection of GaN/AlN MQW structures grown using the IS, GS, and GI techniques, respectively.

Image of FIG. 5.
FIG. 5.

Room-temperature CL spectra from GaN/AlN MQW structures grown using the IS, GS, and GI techniques, respectively.

Image of FIG. 6.
FIG. 6.

Band diagram of GaN/AlN QWs in a superlattice with 3-nm-thick AlN barriers and (a) 4-ML-thick or (b) 8-ML-thick GaN QWs.

Image of FIG. 7.
FIG. 7.

Low-temperature normalized PL spectra of GaN/AlN MQW structures with 3-nm-thick AlN barriers and different GaN QW thicknesses. In the inset, energy location of the low-temperature PL peak as a function of the QW thickness. The solid line is a simulation assuming a polarization discontinuity .

Image of FIG. 8.
FIG. 8.

Low-temperature luminescence from a GaN/AlN MQW structure (sample E935): (a) PL spectrum and CL map around (b) 4.00 eV, (c) 3.68 eV, and (d) 3.78 eV. The energy window was , and the acceleration voltage was 10 keV for all the measurements. Clearer regions correspond to higher CL intensity.

Image of FIG. 9.
FIG. 9.

Low-temperature CL map of a GaN/AlN MQW structure (sample E1042) grown under Ga accumulation conditions: (a) CL spectrum, (b) surface morphology image in the scanning electron microscope, and CL map around (c) 3.82, and (d) 3.97 eV. The energy window was , and the acceleration voltage was 10 keV for all the measurements. Clearer regions correspond to higher CL intensity.

Image of FIG. 10.
FIG. 10.

Room-temperature TM-polarized ISB absorption spectra from Si-doped GaN/AlN MQW structures with 3-nm-thick AlN barriers and different GaN QW thicknesses.

Image of FIG. 11.
FIG. 11.

Variation in the and ISB transition energy as a function of the QW thickness in GaN/AlN superlattices with 3 nm thick AlN barriers. Triangles indicate experimental data and solid and dashed lines correspond to theoretical calculations assuming the structure fully strained on AlN and on GaN, respectively.

Image of FIG. 12.
FIG. 12.

Photovoltaic response of GaN/AlN MQW structures measured as a function of temperature.

Image of FIG. 13.
FIG. 13.

AFM surface analysis of (a) GaN-on-sapphire, (b) -on-sapphire, (c) -on-sapphire, and (d) AlN-on-sapphire templates, and of 20-period GaN/AlN (1.5/3 nm) MQW structures grown on (e) GaN-on-sapphire, (f) -on-sapphire, (g) -on-sapphire, and (h) AlN-on-sapphire templates.

Image of FIG. 14.
FIG. 14.

Reciprocal space map around the (10–15) x-ray reflection of GaN/AlN MQW structures grown (a) on GaN and (b) on AlN templates.

Image of FIG. 15.
FIG. 15.

Room-temperature TM-polarized ISB absorption spectra from Si-doped GaN/AlN (1.5/1.5 nm) MQW structures grown on various -on-sapphire templates.

Image of FIG. 16.
FIG. 16.

RHEED intensity variation induced by Ga desorption from GaN at different substrate temperatures.

Image of FIG. 17.
FIG. 17.

(a) Low-temperature PL spectra from GaN/AlN MQW structures grown at different substrate temperatures. (b) Low-temperature photovoltaic response of QWIPs fabricated on GaN/AlN MQW structures grown at different substrate temperatures.

Image of FIG. 18.
FIG. 18.

Room-temperature TM-polarized ISB absorption spectra of Si-doped GaN/AlN (1.5/3 nm) MQW structures grown doped in the QWs, in the barriers, in the middle of the wells, in the middle of the barriers, and undoped.

Image of FIG. 19.
FIG. 19.

Room-temperature TM-polarized ISB absorption spectra of nonintentionally doped GaN/AlN (1.5/1.5 nm) MQW structures finished with a 50 nm thick cap layer with different Al mole fractions.

Image of FIG. 20.
FIG. 20.

Band diagram of nonintentionally doped GaN/AlN (1.5/1.5 nm) MQW structures with (a) AlN cap layer and (b) GaN cap layer.

Tables

Generic image for table
Table I.

Description of a series of samples grown by different methods (GS: Ga as a surfactant; IS: In as a surfactant; and GI: Ga and Al as surfactants with growth interruption after the AlN barriers): QW thickness measured by HRXRD, AFM rms surface roughness measured in a , and intensity and FWHM of the -scan of the (0002) XRD of the superlattice and of the GaN buffer layer.

Generic image for table
Table II.

Material parameters used in the theoretical calculations. Data indicated with were corrected to achieve a good fit with the experimental results.

Generic image for table
Table III.

GaN/AlN MQW structures with an AlN barrier thickness of 3 nm and variable QW thickness. The value of QW thickness in the table corresponds to the nominal value except for the samples indicated by (1), which were measured by HRXRD or HRTEM. The PL measurements were performed at , and the main PL peak is indicated in bold.

Generic image for table
Table IV.

Series of GaN/AlN MQW structures grown on different templates: Al mole fraction of the substrate, FWHM of the -scan of the superlattice (10–15) x-ray reflection, PL peak energy and FWHM for the transition corresponding to 5 ML QW thickness, ISB absorption peak energy and FWHM, and magnitude of the ISB absorption per reflection. Note that the absorption spectrum consists of multiple peaks, and the ISB absorption FWHM values in this table correspond to the average value of a single peak.

Generic image for table
Table V.

Series of GaN/AlN MQW structures with different Si doping locations: Si location, FWHM of the -scan of the superlattice (0002) x-ray reflection, PL peak energy and FWHM for the transition corresponding to 5 ML QW thickness, ISB absorption energy and FWHM, and magnitude of the ISB absorption per reflection. Note that the absorption spectrum consists of multiple peaks, and the ISB absorption FWHM values in this table correspond to the average value of a single peak.

Generic image for table
Table VI.

Series of nonintentionally doped GaN/AlN (1.5/1.5 nm) MQW structures capped with 50 nm of with different Al mole fractions.

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/content/aip/journal/jap/104/9/10.1063/1.3003507
2008-11-04
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: GaN/AlN short-period superlattices for intersubband optoelectronics: A systematic study of their epitaxial growth, design, and performance
http://aip.metastore.ingenta.com/content/aip/journal/jap/104/9/10.1063/1.3003507
10.1063/1.3003507
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