Insulating GaN:Zn layers grown by hydride vapor phase epitaxy on SiC substrates

Kuznetsov, N. A.; Николаев, А. Е.; Zubrilov, A. S.; Melnik, Yu.; Dmitriev, V.

doi:10.1063/1.125256

Cited by 64 publications

(35 citation statements)

References 22 publications

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“…͑ii͒ The Hall mobility of samples with resistivity about 3ϫ10 3 ⍀ cm shows that a scattering on charged dislocations dominates ( H ϳT x , xϭ0.9 and 0.5͒ in contradiction to lower resistive sample ͑ϭ32 ⍀ cm͒ for which phonon scattering dominates (xϭϪ1.4).…”

Section: ͓S0003-6951͑00͒02825-4͔mentioning

confidence: 96%

“…1 Another possibility to obtain high resistive GaN layers is by acceptor doping. MBE grown C-doped layers 2 and hydride vapor phse epitaxial Zn-doped layers 3 with resistivity of 10 6 and 10 12 ⍀ cm, respectively, have been reported. Unfortunately, carrier concentration and mobility data on samples with resistivity higher than 14 ⍀ cm are not present in the literature due to the use of conductive substrates, 3 or unmeasurable Hall coefficients.…”

Section: ͓S0003-6951͑00͒02825-4͔mentioning

confidence: 99%

“…However, not much is reported about their preparation and transport properties. Layers with resistivity of 14, 3ϫ10 3 , and 10 6 ⍀ cm were previously prepared by varying the stoichiometry during molecular beam epitaxial ͑MBE͒ growth. 1 Another possibility to obtain high resistive GaN layers is by acceptor doping.…”

Section: ͓S0003-6951͑00͒02825-4͔mentioning

confidence: 99%

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Conductivity and Hall-effect in highly resistive GaN layers

Kordoš¹,

Javorka²,

Morvič

et al. 2000

Applied Physics Letters

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Highly resistive GaN layers grown by molecular beam epitaxy are characterized by temperature dependent conductivity and Hall effect measurements. Samples with 300 Х3ϫ10 3 ⍀ cm show room temperature Hall mobility of 22 and 35 cm 2 V Ϫ1 s Ϫ1 and have a temperature dependence H ϳT x with xϭ0.9 and 0.5. This is in contradiction to a sample with 300 Х32 ⍀ cm which has a room temperature mobility of 310 cm 2 V Ϫ1 s Ϫ1 and a H ϳT x with xϭϪ1.4. The same activation energy of 0.23 eV, attributed to donor-like defects, is found for all three samples investigated. Temperature dependent conductivity data can be reasonably fitted considering band conduction. The presence of various hopping mechanisms is discussed. © 2000 American Institute of Physics. ͓S0003-6951͑00͒02825-4͔Highly resistive GaN buffer layers are important for field-effect transistor and high electron mobility transistor structures to avoid a parallel conductive channel that degrades device performance. However, not much is reported about their preparation and transport properties. Layers with resistivity of 14, 3ϫ10 3 , and 10 6 ⍀ cm were previously prepared by varying the stoichiometry during molecular beam epitaxial ͑MBE͒ growth.1 Another possibility to obtain high resistive GaN layers is by acceptor doping. MBE grown C-doped layers 2 and hydride vapor phse epitaxial Zn-doped layers 3 with resistivity of 10 6 and 10 12 ⍀ cm, respectively, have been reported. Unfortunately, carrier concentration and mobility data on samples with resistivity higher than 14 ⍀ cm are not present in the literature due to the use of conductive substrates, 3 or unmeasurable Hall coefficients. 1,4Hopping conduction, with extremely low Hall mobility H Ͻ1 cm 2 V Ϫ1 s Ϫ1, is assumed to be responsible for the latter case.1,5 When the concentrations of the autodoping centers and the deep defects are comparable, the layer becomes highly resistive and conduction by hopping among deep centers might occur. Additional models taking into account scattering on charged dislocations resulting in reduced mobility have been proposed. 6,7 To extend the knowledge of carrier transport behavior in GaN layers, we report in this letter on the temperature dependent conductivity and Hall effect measurements on highly resistive GaN layers grown by MBE.The undoped GaN layers were grown on sapphire substrates by MBE using a radio frequency atomic nitrogen plasma source.8 A low temperature AlN buffer was grown after nitridation of the sapphire. The substrate temperature was then increased to 750°C for the 2-m-thick GaN growth which was done under slightly Ga-rich flux ratios. High resolution x-ray diffraction measurements showed a reasonable layer quality with Х7 arc min full width at half maximum of the ͑0002͒ scan.9 Samples of about 6ϫ6 mm 2 were cut from each wafer and In contacts were alloyed at 850°C after appropriate surface cleaning. The ohmic behavior of the contacts was confirmed by current-voltage characteristics. Accurate temperature dependent conductivity and low magnetic field (Bϭ0.5 T͒ Hall eff...

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Section: ͓S0003-6951͑00͒02825-4͔mentioning

confidence: 96%

Section: ͓S0003-6951͑00͒02825-4͔mentioning

confidence: 99%

See 1 more Smart Citation

Conductivity and Hall-effect in highly resistive GaN layers

Kordoš¹,

Javorka²,

Morvič

et al. 2000

Applied Physics Letters

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“…AlGaN/GaN High Electron Mobility Transistors (HEMTs) need for optimal performance highly resistive GaN layers to avoid parallel conductivity, thereby enhancing the device pinch-off. In general, there are two distinct methods of growing resistive GaN layers by MOCVD: using acceptor doping (Fe, Mg, Zn) [2,3] or optimizing growth conditions [4]. For application in HEMT devices the first method is not desirable because of the reduction of the mobility due to introduction of additional scattering centers.…”

Section: Introductionmentioning

confidence: 99%

Resistivity control of unintentionally doped GaN films

Grzegorczyk¹,

Macht

Hageman

et al. 2005

phys. stat. sol. (c)

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GaN epilayers were grown on sapphire substrates via low temperature GaN and AlN nucleation layers (NL) by metalorganic chemical vapor phase epitaxy (MOCVD). The morphology of the individual NLs strongly depends on the carrier gas used during the growth and recrystallization and this is the key factor for control of the resistivity of the GaN layer grown on it. The GaN nucleation layer grown in presence of N 2 has a higher density of islands with a statistically smaller diameter than the samples grown in H 2 atmosphere. The NL grown in N 2 enables the growth GaN with a sheet resistivity higher than 3×104 Ω⋅cm as opposed to a 0.5 Ω cm value obtained for the NL grown in H 2 . Introduction of an additional intermediate (IL) low temperature (GaN or AlN) nucleation layer changes the GaN epilayer resistivity to about 50 Ω⋅cm, regardless of the carrier gas used during the growth of the IL. Defect selective etching demonstrated that control of the type and density of the dislocations in GaN enables the growth of highly resistive layers without any intentional acceptor doping (Mg, Zn). It will be demonstrated that by changing the ratio of edge type to screw dislocations the resistivity of the layer can be changed by a few orders of magnitude.

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“…the pyroelectric sensors and the surface acoustic wave(SAW) devices due to the inherent strong polarization effects of hexagonal lattices. For electromechanical application of nitride materials, the GaN films for SAW devices were doped with Mg, and Zn to compensate the oxygen impurities for low loss applications [1]. Since an undoped GaN layer exhibits a high electrical conductivity, several reports showed the increased insertion loss that is detrimental for the SAW devices which were fabricated on an epitaxially grown GaN thin film.…”

mentioning

confidence: 99%

Two‐step temperature ramping technique in MOCVD GaN films with high electromechanical coupling coefficients

Lee¹,

Park²,

Bae

et al. 2003

phys. stat. sol. (c)

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Undoped GaN films for high electromechanical coefficient were grown by controlling the size of nucleation sites through a special two step growth method. The film grown by this sequence exhibited the sheet resistance of up to 109 Ω/sq with mirror-like surface morphology. The high resistance of undoped GaN film is thought to be due to the promoted misorientation of nuclei in a or c axis and the formation of deep trap levels in the bandgap when a GaN film was grown during ramping temperature from 950 to 1020 °C for 3 min in the initial growth stage. The fabricated saw filter on semi-insulating GaN exhibited a high velocity of 5342 m/s at center frequencies of 133.57 MHz and an electromechanical coupling coefficient (k 2 ) of about 0.763% which was enhanced due to the improvement of surface morphology with high sheet resistance by the two step ramping technique. 1 Introduction Group III-nitride semiconductors and their ternary solid solutions are very promissing as the candidates for both short wavelength optoelectronics and power electronic devices. The AlGaN/GaN heterostructure field effect transistors have a great potential for future high-frequency and high-power applications because of the intrinsic advantages of materials such as high breakdown voltage and high electron peak velocity. These III-nitride materials are also suited for application in high temperature piezoelectronics, i.e. the pyroelectric sensors and the surface acoustic wave(SAW) devices due to the inherent strong polarization effects of hexagonal lattices. For electromechanical application of nitride materials, the GaN films for SAW devices were doped with Mg, and Zn to compensate the oxygen impurities for low loss applications [1]. Since an undoped GaN layer exhibits a high electrical conductivity, several reports showed the increased insertion loss that is detrimental for the SAW devices which were fabricated on an epitaxially grown GaN thin film. Also, AlGaN/GaN HFETs require a highly resistive GaN layer both for the purpose of device isolation and for achieving good rf performance. A successful preparation of highly resistive GaN films was recently reported simply by adjusting the growth parameters, such as III/V ratio, growth pressure, growth temperature, and annealing time [2 -4]. In this work, we report on the MOCVD growth of the undoped GaN film, which is suitable for electromechanical applications, by controlling the size of nucleation sites through a special two-step growth method. A high electromechanical coefficient was demonstrated in the fabricated GaN SAW filter.

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Insulating GaN:Zn layers grown by hydride vapor phase epitaxy on SiC substrates

Cited by 64 publications

References 22 publications

Conductivity and Hall-effect in highly resistive GaN layers

Conductivity and Hall-effect in highly resistive GaN layers

Resistivity control of unintentionally doped GaN films

Two‐step temperature ramping technique in MOCVD GaN films with high electromechanical coupling coefficients

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