Nitride based high power devices: design and fabrication issues

Bandić, Zvonimir; Piquette, E. C.; Bridger, P. M.; Beach, Robin; Kuech, T. F.; McGill, T. C.

doi:10.1016/s0038-1101(98)00227-5

Cited by 20 publications

(14 citation statements)

References 5 publications

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“…Since the thickness of the standoff region sets the resistivity of the device, it will determine power dissipation and maximum current density of the device. 2,3 In previous studies, Schottky diodes have been fabricated on GaN using a variety of elemental metals including Pd and Pt, 4,5 , Au, Cr, and Ni,6,7 , and Mo and W. 8 More details on the metal-GaN contact technology can be found in Ref. 9.…”

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confidence: 99%

“…The mesa edge termination was produced by chemically assisted ion beam etching, using Xe ions accelerated with 1000 V, and 25 sccm of Cl 2 flow. 2,3 For the metal field plate devices, SiO 2 was sputtered using SiO 2 targets and 10 sccm of O 2 flow, and then patterned. The ideality factor of the diodes ranged between 1.6 and 4.…”

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confidence: 99%

“…A high critical field indicates feasability of GaN as a material for a variety of unipolar and bipolar devices. 2,3 Furthermore, assuming that the critical field for electric breakdown approximately scales as the square of the band gap, even higher critical fields can be expected for AlGaN. The lack of a suitable conductive GaN substrate which can provide large area back ohmic contact and therefore uniform current spreading, can be circumvented by using highly doped layers underneath the active standoff layer.…”

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confidence: 99%

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High voltage (450 V) GaN Schottky rectifiers

Bandić

Bridger

Piquette

et al. 1999

Applied Physics Letters

153

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We fabricated high standoff voltage ͑450 V͒ Schottky rectifiers on hydride vapor phase epitaxy grown GaN on sapphire substrate. Several Schottky device geometries were investigated, including lateral geometry with rectangular and circular contacts, mesa devices, and Schottky metal field plate overlapping a SiO 2 layer. The best devices were characterized by an ON-state voltage of 4.2 V at a current density of 100 A/cm 2 and a saturation current density of 10 Ϫ5 A/cm 2 at a reverse bias of 100 V. From the measured breakdown voltage we estimated the critical field for electric breakdown in GaN to be (2.2Ϯ0.7)ϫ10 6 V/cm. This value for the critical field is a lower limit since most of the devices exhibited abrupt and premature breakdown associated with corner and edge effects. © 1999 American Institute of Physics. ͓S0003-6951͑99͒02409-2͔Wide band gap materials, primarily SiC and GaN, have recently attracted a lot of interest for applications in high power and high temperature electronics. Although the processing technology for SiC is more mature, GaN offers several advantages. First, there are various device possibilities using GaN/AlGaN heterojunctions which are not available in the SiC system. Second, the availability of cheap and efficient hydride vapor phase epitaxy ͑HVPE͒ growth technology achieving growth rates in excess of 100 m/h, have produced thick, high quality GaN layers on sapphire. 1 Third, by using AlGaN layers, one can take advantage of a larger band gap to achieve higher critical electric fields than in GaN alone.In this study, we focus on the fabrication of high voltage, GaN based Schottky rectifiers and the measurement of the critical field for electric breakdown. The critical field for electric breakdown is one of the most significant parameters in the design and performance of high power devices. It directly influences the required thickness of the standoff region in the Schottky rectifier and bipolar devices, such as the thyristor. Since the thickness of the standoff region sets the resistivity of the device, it will determine power dissipation and maximum current density of the device. 2,3 In previous studies, Schottky diodes have been fabricated on GaN using a variety of elemental metals including Pd and Pt, 4,5 , Au, Cr, and Ni,6,7 , and Mo and W. 8 More details on the metal-GaN contact technology can be found in Ref. 9.In this work, Schottky rectifiers were fabricated on 8-10 m thick GaN layers grown by HVPE on sapphire, where the electron concentration changes with the distance from the GaN/sapphire interface. We carried out conductivity and Hall measurements on a series of HVPE GaN films of varying thickness ranging from 0.07 to 9.2 m, and fitted the data to a two layer model. [10][11][12][13] From the model, we concluded that the GaN films consisted of a low conductivity, low electron concentration, 8-10 m thick top layer on a very thin (Ͻ100 nm), highly conductive, high electron concentration bottom layer. The electron concentrations and mobilities in the thin interface layer and thic...

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High voltage (450 V) GaN Schottky rectifiers

Bandić

Bridger

Piquette

et al. 1999

Applied Physics Letters

153

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“…1 Further applications of nitrides are expected in the arena of high power and high temperature devices, [2][3][4] as well as solar blind ultraviolet detectors. 5 It has been recently demonstrated that the large intrinsic piezoelectric coefficients of GaN and AlN are responsible for an anomalously large concentration of two-dimensional electron gas at the AlGaN/GaN interface in GaN/AlGaN heterojunction field effect transistors ͑HFET͒.…”

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confidence: 99%

Electric force microscopy of induced charges and surface potentials in GaN modified by light and strain

Bridger

Bandić

Piquette

et al. 1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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We have studied molecular beam epitaxy grown GaN films using electric force microscopy to detect sub-1 m regions of electric field gradient and surface potential variations associated with GaN extended defects. The large piezoelectric coefficients of GaN together with strain introduced by crystalline imperfections produce variation in piezoelectrically induced electric fields around these defects. The consequent spatial rearrangement of charges can be detected by electrostatic force microscopy, and can be additionally modified by externally applied strain and illumination. The electron force microscopy signal was found to be a function of the applied tip bias, showed reversal under externally applied strain, and was sensitive to above band gap illumination.

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“…[1][2][3][4][5] For these reasons, GaN is currently used for mass-produced light-emitting diodes (LEDs), lasers, and high-frequency devices. [6][7][8][9][10] Metalorganic vapor phase epitaxy (MOVPE) is commonly employed to manufacture GaN films using trimethylgallium (TMGa) and NH 3 as group-III and group-V precursors, respectively.…”

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Kinetic Analysis of GaN-MOVPE via Thickness Profiles in the Gas Flow Direction with Systematically Varied Growth Conditions

Momose

Kamiya

Suzuki

et al. 2016

ECS J. Solid State Sci. Technol.

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We carried out a kinetic analysis of metallorganic vapor phase epitaxy (MOVPE) of GaN to investigate the dependence of the growth rate on the process conditions as a function of residence time of the precursors in the reactor. The wafer was not rotated during growth, allowing us to analyze the thickness profile of the film in the direction of gas flow, and hence the dependence of the growth rate on the residence time. The growth rate is determined mainly by the concentration of the growth species and mass transfer of the growth species to the wafer surface. The growth rate peaked in the flow direction, and the position of this peak could, in most cases, be explained by considering a combination of the linear gas velocity and the time constant for vertical diffusion of trimethylgallium (TMGa) and/or growth species across the NH 3 feed stream to the wafer surface. In some cases this was not possible, indicating that more complex effects were significant. This work is expected to contribute to understanding of the reaction pathways for GaN-MOVPE, and the growth rate data reported here are expected to provide useful benchmarks for growth simulations that combine computational fluid dynamics and reaction models. Gallium nitride (GaN) is a III/V compound semiconductor material with considerable potential for optoelectronic and high-power electronic devices due to its wide bandgap and high breakdown voltage.1-5 For these reasons, GaN is currently used for mass-produced light-emitting diodes (LEDs), lasers, and high-frequency devices. 6-10Metalorganic vapor phase epitaxy (MOVPE) is commonly employed to manufacture GaN films using trimethylgallium (TMGa) and NH 3 as group-III and group-V precursors, respectively. Research into the growth mechanisms involved in GaN-MOVPE in both academic and industrial institutions has found that the reaction chemistry is relatively complicated, consisting of gas-phase reactions followed by surface reactions. [11][12][13][14][15][16][17] This intrinsic complexity of the reactions suggests that it is not straightforward to design optimal reactors for mass production as well as settling the optimal growth conditions via conventional empirical approaches. Therefore, a variety of studies have been carried out with the aim of understanding GaN-MOVPE. Initially, attention mainly focused on identification of intermediate species that are generated from the gas-phase precursors, which contribute to the layer growth. It then became apparent that parasitic reactions in the gas phase resulted in the formation of adducts, even in the non-heated area of the reactor, in addition to those formed in the hot zone in the vicinity of the heated substrate.18,19 Some of these reaction products led to particle formation without contributing to layer growth. [20][21][22] 39 However, a model that can describe the growth behavior consistently in all reactor configurations and for all process conditions remains elusive. This is our concern, and necessitates comprehensive investigation on the behavior of GaN growt...

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Nitride based high power devices: design and fabrication issues

Cited by 20 publications

References 5 publications

High voltage (450 V) GaN Schottky rectifiers

High voltage (450 V) GaN Schottky rectifiers

Electric force microscopy of induced charges and surface potentials in GaN modified by light and strain

Kinetic Analysis of GaN-MOVPE via Thickness Profiles in the Gas Flow Direction with Systematically Varied Growth Conditions

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