Optical properties of N-polar GaN: The possible role of nitrogen vacancy-related defects

Tatarczak, Piotr; Turski, Henryk; Korona, K. P.; Grzanka, Ewa; Skierbiszewski, C.; Wysmołek, A.

doi:10.1016/j.apsusc.2021.150734

Cited by 11 publications

(6 citation statements)

References 42 publications

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“…Nevertheless, further enhancement of the internal quantum efficiency of GaN/(Al,Ga)N heterostructures grown by MBE will necessarily require to minimize the density of point defects. Two approaches currently under developments are the growth of dedicated buffer layers to bury point defects [96,101] and the use of different growth conditions [16,102].…”

Section: Discussionmentioning

confidence: 99%

“…Yet, establishing other strategies to further decrease the density of point defects in GaN/(Al,Ga)N heteorostructures would certainly benefit to the performance of nitride-based ultraviolet light emitting devices [7], transistors [8][9][10][11], and future devices. For the epitaxial growth of semiconductors, it is well known that the crystal orientation influences not only the surface morphology [12][13][14][15][16], but also the incorporation of impurities and the formation of nonradiative point defects [17][18][19]. For instance, a dramatic case are (In,Ga)N/GaN QWs grown by plasma-assisted molecular beam epitaxy (PA-MBE), which may not exhibit any detectable luminescence even at 10 K if grown N-polar [i.e.…”

Section: Introductionmentioning

confidence: 99%

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Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Auzelle,

Sinito,

Lähnemann

et al. 2021

Preprint

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We explore and systematically compare the morphological, structural and optical properties of GaN/(Al,Ga)N multiple quantum wells (MQWs) grown by plasma-assisted molecular beam epitaxy (PA-MBE) on freestanding GaN(0001) and GaN(000 1) substrates. Samples of different polarity are found to be on par in terms of their morphological and structural perfection and exhibit essentially identical quantum well widths and Al content. Regardless of the crystal orientation, the exciton decay in the MQWs at 10 K is dominantly radiative and the photoluminescence (PL) energy follows the quantum confined Stark effect (QCSE) for different quantum well widths. A prominent free-to-bound transition involving interface shallow donors is, however, visible for the N-polar MQWs. At room-temperature, in contrast, the exciton decay in all samples is dominated by nonradiative recombination taking place at point defects, presumably Ca or V 𝑁 located at the bottom QW interface. Remarkably, the N-polar MQWs exhibit a higher PL intensity and longer decay times than the Gapolar MQWs at room-temperature. This improved internal quantum efficiency is attributed to the beneficial orientation of the internal electric field that effectively reduces the capture rate of minority carriers by interface trap states.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Auzelle,

Sinito,

Lähnemann

et al. 2021

Preprint

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“…In contrast to MOCVD growth, GaN layers are typically grown on on-axis substrates at a much lower temperature under typical metal-rich conditions using a plasma-assisted molecular beam epitaxy (PA-MBE) technique. Even though N-polar GaN with a smooth surface has been shown to grow on vicinal GaN substrates using PA-MBE, the N-rich conditions are recommended to suppress the surface undulations and reduce the roughness [17][18][19]. However, this leads to oxygen contamination that is an order of magnitude higher than that grown under Ga-rich conditions [19].…”

Section: Introductionmentioning

confidence: 99%

“…Even though N-polar GaN with a smooth surface has been shown to grow on vicinal GaN substrates using PA-MBE, the N-rich conditions are recommended to suppress the surface undulations and reduce the roughness [17][18][19]. However, this leads to oxygen contamination that is an order of magnitude higher than that grown under Ga-rich conditions [19]. In addition, the formation of a Ga-metallic layer on the surface under Garich conditions enhances adatom diffusion and improves surface smoothness [20].…”

Section: Introductionmentioning

confidence: 99%

Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

Huo¹,

Lingaparthi²,

Dharmarasu³

et al. 2023

J. Phys. D: Appl. Phys.

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The surface morphology evolution of N-polar GaN with growth time was investigated and compared with Ga-polar GaN. N-polar GaN directly grown on SiC substrates was found to have slower three-dimensional (3D) to two-dimensional (2D) growth transformation and lesser coalescence than the Ga-polar counterpart, resulting in rougher surface morphology, whereas the AlN nucleation layer (NL) accelerated 3D to 2D transformation, resulting in smoother surface morphology. N-polar GaN was found to have mound-type surface morphology with clustered atomic steps, unlike the regular screw-type dislocation-mediated step-flow growth observed for Ga-polar GaN. This was explained by the lower diffusion of adatoms on the N-polar surface due to its higher surface energy and higher Ehrlich-Schwoebel barrier (ESB). In addition, the increased III/V ratio in N-polar GaN growth was found to reduce the surface roughness from 2.4 nm to 1 nm. Without Si doping, the N-polar GaN HEMT heterostructures grown under optimized conditions with smoother surface morphologies exhibited sheet carrier density of 0.91 × 1013 cm-2 and mobility of 1220 cm2/V∙s. With Si δ-doping, the sheet carrier density was increased to 1.28 × 1013 cm-2 while the mobility was reduced to 1030 cm2/V∙s. These results are comparable to the state-of-the-art data of PA-MBE-grown N-polar GaN HEMT heterostructures on SiC substrates.

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“…However, the sensing performance of these fabricated APS and PPS devices exhibited a high dark current, low responsivity, and poor UVRR, which was attributed to their low-quality epitaxial layer and high defect density. A high dark current caused by trap-assisted leakage through defects deteriorates the photo-response characteristics of UV photodetectors, resulting in poor detection capability [ 19 , 20 , 21 , 22 ]. Moreover, during imaging processes, the high noise (fixed pattern and temporal) caused by the defects decreases the signal-to-noise ratio (SNR), adversely affecting the quality of the sensing image [ 11 , 22 , 23 , 24 , 25 , 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

Interface Trap Effect on the n-Channel GaN Schottky Barrier-Metal–Oxide Semiconductor Field-Effect Transistor for Ultraviolet Optoelectronic Integration

Park,

Kim,

Hahm

2023

Nanomaterials

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Ultraviolet (UV) photodetectors are key devices required in the industrial, military, space, environmental, and biological fields. The Schottky barrier (SB)-MOSFET, with its high hole and electron barrier, and given its extremely low dark current, has broad development prospects in the optoelectronics field. We analyze the effects of trap states on the output characteristics of an inversion mode n-channel GaN SB-MOSFET using TCAD simulations. At the oxide/GaN interface below the gate, it was demonstrated that shallow donor-like traps were responsible for degrading the subthreshold swing (SS) and off-state current density (Ioff), while deep donor-like traps below the Fermi energy level were insignificant. In addition, shallow acceptor-like traps shifted the threshold voltage (Vt) positively and deteriorated the SS and on-state current density (Ion), while deep acceptor-like traps acted on a fixed charge. The output characteristics of the GaN SB-MOSFET were related to the resistive GaN path and the tunneling rate due to the traps at the metal (source, drain)/GaN interface. For the UV responses, the main mechanism for the negative Vt shift and the increases in the Ion and spectral responsivity was related to the photo-gating effect caused by light-generated holes trapped in the shallow trap states. These results will provide insights for UV detection technology and for a high-performance monolithic integration of the GaN SB-MOSFET.

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Optical properties of N-polar GaN: The possible role of nitrogen vacancy-related defects

Cited by 11 publications

References 42 publications

Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Surface morphology evolution of N-polar GaN on SiC for HEMT heterostructures grown by plasma-assisted molecular beam epitaxy

Interface Trap Effect on the n-Channel GaN Schottky Barrier-Metal–Oxide Semiconductor Field-Effect Transistor for Ultraviolet Optoelectronic Integration

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