Competition between band gap and yellow luminescence in undoped GaN grown by MOVPE on sapphire substrate

Xu, Houqiang; Bell, A.; Wang, Z.G.; Okada, Yoshitaka; Kawabe, Mitsuo; Harrison, I.; Foxon, C.T.

doi:10.1016/s0022-0248(00)00927-1

Cited by 26 publications

(25 citation statements)

References 29 publications

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“…So the point defect V Ga was attributed to the YL in GaN. This widely accepted suggestion was supported by some experimental results [16,17]. The schematics of atomic arrangements on the (11-20) a-plane GaN surface and the position of V Ga are shown in Figure 7.…”

Section: Yl Bands So the Yl Could Be Enhanced By The Transitions Betmentioning

confidence: 59%

“…The results showed that the XRC-FWHM value of the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) plane along the c-axis direction and m-axis direction increased with increasing SiH 4 flow rate, which demonstrated that the crystalline quality along the c-axis direction slightly decreased. It means that the dislocation density increases with increasing SiH 4 flow rate.…”

Section: Resultsmentioning

confidence: 96%

“…Masayuki et al analyzed a non-polar type a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) AlGaN/GaN HFET free from polarization, and concluded that the polarization was not formed perpendicular to the heterointerface so the device could allow nearly normally-off operations [4]. However, the extended defect densities in non-polar a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) GaN were yet very high according to the state-of-the-art of material growth technology. For the a-plane (11-20) GaN on r-plane (1-102) grown by metal organic chemical vapor deposition (MOCVD), there occurred a TD density of 3×10 10 cm −2 and a basal stacking fault density of 3.5×10 5 cm −1 [5].…”

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confidence: 99%

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Optical and electrical properties of Si-doped in a-plane GaN grown on r-plane sapphire

Zhou

Yang

et al. 2010

Sci. China Technol. Sci.

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a-plane GaN grown on (1-102) r-plane sapphire substrate was obtained by metal organic chemical vapor deposition. The optical and electrical properties of the Si-doped a-plane GaN films were investigated by photoluminescence spectroscopy, high-resolution X-ray diffraction, atomic force microscopy and Hall measurement. The results showed that the morphology and the crystal quality slightly degraded with Si doping. The yellow luminescence was enhanced with increasing the flow rate of the SiH 4 . The significant improvement of the mobility should associate with some of the vacancy filled with the Si. GaN, nonpolar, dislocation, photoluminescenceCitation: Xu S R, Zhou X W, Hao Y, et al. Optical and electrical properties of Si-doped in a-plane GaN grown on r-plane sapphire.AlGaN/GaN heterostructures have shown the excellent properties in advanced power and optoelectronic devices, such as high electron mobility transistors (HEMTs) and light-emitting diodes (LEDs). It has also been found that the wurtzite phase AlGaN/GaN exhibits huge spontaneous and piezoelectronic polarization effects that negatively impact the performance of LED. It is due to that the spatial separation of electrons and holes in quantum well with c-axis orientation seriously reduces the oscillator strength thereby causes a redshift of emission wavelength, which is called the quantum confined Stark effect. On the other hand, the extra-ordinarily high polarization charges make it difficult to enable normally-off operations on the c-plane face. To circumvent this problem, a material growth with non-polar crystal orientation was developed [1-3]. Masayuki et al. analyzed a non-polar type a-plane (11-20) AlGaN/GaN HFET free from polarization, and concluded that the polarization was not formed perpendicular to the heterointerface so the device could allow nearly normally-off operations [4]. However, the extended defect densities in non-polar a-plane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) GaN were yet very high according to the state-of-the-art of material growth technology. For the a-plane (11-20) GaN on r-plane (1-102) grown by metal organic chemical vapor deposition (MOCVD), there occurred a TD density of 3×10 10 cm −2 and a basal stacking fault density of 3.5×10 5 cm −1 [5]. So the electron mobility of the as-grown a-plane GaN films was very low. It was only 5.14 cm 2 /Vs in Masayuki Kuroda's work. In this paper, a-plane GaN films with different Si doping concentrations were grown by MOCVD. Their optical, surface morphology, structural and electrical properties were studied by photoluminescence spectrum (PL), atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD) and Hall measurements.

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Section: Yl Bands So the Yl Could Be Enhanced By The Transitions Betmentioning

confidence: 59%

Section: Resultsmentioning

confidence: 96%

mentioning

confidence: 99%

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Optical and electrical properties of Si-doped in a-plane GaN grown on r-plane sapphire

Zhou

Yang

et al. 2010

Sci. China Technol. Sci.

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“…10 A number of researchers attribute it to a V Ga -O N complex. [11][12][13][14] Rather, most of these mechanisms may be present at the same time; however, at higher C doping, a higher energy band appears in the spectrum. 8 Fabrication of large area GaN substrates with a relatively low concentration of impurities (still barely available) has so far been done by halide vapor phase epitaxy (HVPE).…”

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confidence: 99%

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

Khromov

Hemmingsson

Ḿonemar

et al. 2014

Journal of Applied Physics

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Optical and structural studies of homoepitaxially grown m-plane GaN Appl. Phys. Lett. 100, 172108 (2012) Freestanding bulk C-doped GaN wafers grown by halide vapor phase epitaxy are studied by optical spectroscopy and electron microscopy. Significant changes of the near band gap (NBG) emission as well as an enhancement of yellow luminescence have been found with increasing C doping from 5 Â 10 16 cm À3 to 6 Â 10 17 cm À3. Cathodoluminescence mapping reveals hexagonal domain structures (pits) with high oxygen concentrations formed during the growth. NBG emission within the pits even at high C concentration is dominated by a rather broad line at $3.47 eV typical for n-type GaN. In the area without pits, quenching of the donor bound exciton (DBE) spectrum at moderate C doping levels of 1-2 Â 10 17 cm À3 is observed along with the appearance of two acceptor bound exciton lines typical for Mg-doped GaN. The DBE ionization due to local electric fields in compensated GaN may explain the transformation of the NBG emission. V C 2014 AIP Publishing LLC.

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“…Several researchers reported enhancement of the YL due to C doping [59], [60]. Some others reported its relation to Gallium vacancies V Ga [61] or to recombination between O N and V Ga [62], [63]. The origin of the YL therefore remains controversial.…”

Section: Yellow Line (Yl)mentioning

confidence: 99%

Doping effects on the structural and optical properties of GaN

Khromov¹

2013

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Today there is a strong drive towards higher efficiency light emitters and devices for power electronics based on GaN and its ternary compounds. Device performance can be improved in several ways on the material level. Development of bulk GaN to substitute sapphire and SiC as substrate materials can allow lower defect density epitaxial GaN layers to be grown. Using nonpolar homoepitaxial layers alleviates the problem of polarization fields present in polar GaN epilayers. This thesis advances the field by attacking outstanding problems related to doping and its influence on structural and optical properties of GaN. Optical and structural investigations were performed on bulk GaN grown by halide vapor phase epitaxy (HVPE) and on polar and nonpolar epitaxial GaN grown by metal organic chemical vapor deposition (MOCVD), doped with different impurities: Mg, Si, O or C. Optical characterization was done using photoluminescence (PL), time-resolved photoluminescence (TRPL), and cathodoluminescence (CL) in-situ scanning electron microscope, whereas structural properties were studied by means of transmission electron microscopy (TEM) and atom probe tomography (APT Simultaneous doping by Si and O was studied for HVPE grown bulk GaN. Doping with O concentration from 10 17 cm -3 leads to a decrease in the Si concentration to less than 10 16 cm -3 . Si incorporation is believed to be suppressed by the competing Ga-vacancy-O incorporation process. Bandgap narrowing by 6 meV due to high doping was observed. Donor bound exciton (DBE) lifetime was obtained from TPRL experimental data and it is found to decrease with increasing doping. In non-polar m-plane homoepitaxial GaN Si doping influences the SF-related luminescence. At moderate Si concentrations excitons are bound to ii the impurity atoms or impurity-SF complex. Proximity of impurity atoms changes the potential for SF creating localization for charge carriers resulting in SF-related emission. At dopant concentrations higher than the Mott limit screening destroys the carrier interaction and, thus, the exciton localization at impurity-SF complex.Finally, C-doped HVPE grown bulk GaN layers were studied by TEM, CL, and TRPL. Enhanced yellow line (YL) luminescence was observed with increasing C doping. Stability of YL in a wide temperature range (5-300 K) confirms that YL is due to a deep defect, likely C N -O N complex. Low-temperature CL mapping reveals a pit-like structure with different luminescence properties in different areas. DBE emission dominates in CL spectra within the pits while in pit-free areas, in contrast, two ABE lines typical for Mg-doped GaN are observed.iii POPULÄRVETENSKAPLIG SAMMANFATTNINGUngefär 20% av all elektricitet som produceras i världen används till belysning. Det betyder att vi kommer att spara mycket energi om vi ersätter nuvarande lågeffektiva glödlampor med starka vita lysdioder (LED), dessutom kommer utsläpp av koldioxid på planeten att minskas. Detta förklarar orsaken till den enorma utvecklingen av LED-industri som har skett under de...

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Competition between band gap and yellow luminescence in undoped GaN grown by MOVPE on sapphire substrate

Cited by 26 publications

References 29 publications

Optical and electrical properties of Si-doped in a-plane GaN grown on r-plane sapphire

Optical and electrical properties of Si-doped in a-plane GaN grown on r-plane sapphire

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

Doping effects on the structural and optical properties of GaN

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