Polar and nonpolar HVPE GaN substrates: impact of doping on the structural, electrical and optical characteristics

Paskova, T.; Preble, E. A.; Hanser, Α.; Evans, K. R.; Kröger, Roland; Paskov, Plamen; Cheng, An-Jen; Park, M.; Grenko, J. A.; Johnson, Mark A.

doi:10.1002/pssc.200880912

Cited by 17 publications

(11 citation statements)

References 8 publications

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“…The free electron concentration, n e , as determined by conventional Hall effect measurements at room temperature showed a nearly complete donor ionization, i. e. the n e scales closely with the Si concentration in an agreement with previous studies. 22 The Ga vacancy density was studied by positron annihilation spectroscopy (PAS). In all samples, no vacancy signal was detected which leads to the conclusion that the Ga vacancy density was below 1×10 15 cm -3 (detection limit of the PAS).…”

Section: A Sample Growth and Characterizationmentioning

confidence: 99%

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

et al. 2017

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The effect of Si doping on the thermal conductivity of bulk GaN was studied both theoretically and experimentally. The thermal conductivity of samples grown by Hydride Phase Vapor Epitaxy (HVPE) with Si concentration ranging from 1.6×1016 to 7×1018 cm-3 was measured at room temperature and above using the 3ω method. The room temperature thermal conductivity was found to decrease with increasing Si concentration. The highest value of 245±5 W/m.K measured for the undoped sample was consistent with the previously reported data for free-standing HVPE grown GaN. In all samples, the thermal conductivity decreased with increasing temperature. In our previous study, we found that the slope of the temperature dependence of the thermal conductivity gradually decreased with increasing Si doping. Additionally, at temperatures above 350 K the thermal conductivity in the highest doped sample (7×1018 cm-3) was higher than that of lower doped samples. In this work, a modified Callaway model adopted for n-type GaN at high temperatures was developed in order to explain such unusual behavior. The experimental data was analyzed with examination of the contributions of all relevant phonon scattering processes. A reasonable match between the measured and theoretically predicted thermal conductivity was obtained. It was found that in n-type GaN with low dislocation densities the phonon-free-electron scattering becomes an important resistive process at higher temperatures. At the highest free electron concentrations, the electronic thermal conductivity was suggested to play a role in addition to the lattice thermal conductivity and compete with the effect of the phonon-point-defect and phonon-free-electron scattering.

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Section: A Sample Growth and Characterizationmentioning

confidence: 99%

Effect of Si doping on the thermal conductivity of bulk GaN at elevated temperatures – theory and experiment

et al. 2017

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“…The use of H 2 carrier gas and its effect on the efficacy of p-type doping with Mg is a point of controversy in the reports due to the formation of Mg-H complexes and the need for thermal annealing that is usually performed in situ directly after the growth. The semi-insulating type of HVPE-GaN was reported by using Fe compensating doping [12], [13], achieving free carrier concentration as low as 5 Â 10 13 cm À3 [13]. The optimization of the HVPE-GaN growth is impeded by the typical complications of crystal growth technology like the multidisciplinary nature and complex multiparameter character of the process.…”

Section: A Hydride Vapor Phase Epitaxymentioning

confidence: 99%

“…The development of substrates with both nonpolar and semipolar surfaces was initiated by utilizing foreign substrates, such as (1-102) sapphire or (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) SiC for a-plane GaN, (100) LiAlO 2 or (1-100) SiC for m-plane GaN, and (100) MgAl 2 O 4 for (10-11)-plane GaN, or (110) MgAl 2 O 4 for (10-13)-plane GaN [59]. The HVPE growth of thick layers GaN has also benefited from the ability for self-separation from some of the above substrates [60].…”

Section: Nonpolar and Semipolar Substrate Developmentmentioning

confidence: 99%

“…There are still unresolved questions like In incorporation efficiency in layers grown on GaN substrates with different surface orientations, resulting in different emission wavelength [as in Fig. 6(d) and (e)] in simultaneously grown samples in the [0001], and [11][12][13][14][15][16][17][18][19][20] directions [78], [84], [85] on GaN substrates. Further knowledge gained on this issue as well as a further increase of the substrate size will allow better control of In incorporation for achieving the desired wavelengths.…”

Section: Paskova Et Al: Gan Substrates For Iii-nitride Devicesmentioning

confidence: 99%

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GaN Substrates for III-Nitride Devices

2010

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| Despite the rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics, their full potential is limited by two primary obstacles: i) a high defect density and biaxial strain due to the heteroepitaxial growth on foreign substrates, which result in lower performance and shortened device lifetime, and ii) a strong built-in electric field due to spontaneous and piezoelectric polarization in the wurtzite structures along the well-established [0001] growth direction for nitrides. Recent advances in the research, development, and commercial production of native GaN substrates with low defect density and high structural and optical quality have opened opportunities to overcome both of these obstacles and have led to significant progress in the development of several optoelectronic and high-power devices. In this paper, the recent achievements in bulk GaN growth development using different approaches are reviewed; comparison of the bulk materials grown in different directions is made; and the current achievements in device performance utilizing native GaN substrate material are summarized.

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“…4 For example, in GaN crystals grown by the hydride (halide) vapour-phase epitaxy (HVPE) an unintentional n-type conductivity originates from the background doping by silicon and oxygen from the quartz elements of the reactor or from the process gases (Paskova et al, 2010). Fe compensating doping allows one to achieve semi-insulating properties of the layer in this growth method (Vaudo et al, 2003) with the the lowest free carrier concentration reported so far 5 · 10 13 cm −3 (Paskova et al, 2009). However, the performance parameters of AlGaN/GaN heterostructure field-effect transistor (HFET) structure formed by depositing a layer of AlGaN on a relatively thick semi-insulating GaN epitaxial layer are greatly improved by replacing a GaN epitaxial layer with a highly resistive AlN epitaxial layer in the device structure, in particularity, parasitic conduction in the GaN epilayer, leakage current through the GaN epilayer, and the channel electrons spillover into the GaN epilayer have been completely eliminated and the drain current collapse has been reduced (Fan et al, 2006).…”

mentioning

confidence: 99%