Impact of residual carbon on two-dimensional electron gas properties in AlxGa1−xN/GaN heterostructure

The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 1018 cm−3) epitaxial layer closest to the substrate and a lower doped layer (3 × 1016 cm−3) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 1018 cm−3) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

Section: à3mentioning

confidence: 99%

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Bergsten

Nilsson

et al. 2015

“…The extent of contamination complexly depends on the growth conditions, including the growth temperature, III/V ratio, gas flow rate, and reactor pressure. 6 In particular, several studies on MOCVD have reported an undesirable increase in carbon concentration in GaN with increasing TMGa flow rate 7 or growth rate. 8 By contrast, a new growth technique called pulsed sputtering deposition (PSD) has recently attracted much attention.…”

mentioning

confidence: 99%

Electrical properties of Si-doped GaN prepared using pulsed sputtering

Arakawa

Ueno

Imabeppu

et al. 2017

In this study, we investigated the basic electrical properties of Si-doped wurtzite GaN films prepared using a low-temperature pulsed sputtering deposition (PSD) process. We found that the electron concentration can be controlled in the range between 1.5 × 1016 and 2.0 × 1020 cm−3. For lightly Si-doped GaN ([Si] = 2.1 × 1016 cm−3), the room temperature (RT) electron mobility was as high as 1008 cm2 V−1 s−1, which was dominantly limited by polar optical phonon scattering. Moreover, we found that heavily Si-doped GaN prepared using PSD exhibited an RT mobility as high as 110 cm2 V−1 s−1 at an electron concentration of 2 × 1020 cm−3, which indicated that the resistivity of this film was almost as small as those of typical transparent conductive oxides such as indium tin oxide. At lower temperatures, the electron mobility increased to 1920 cm2 V−1 s−1 at 136 K, and the temperature dependence was well explained by conventional scattering models. These results indicate that Si-doped GaN prepared using PSD is promising not only for the fabrication of GaN-based power devices but also for use as epitaxial transparent electrode materials for nitride based optical devices.

“…Details of the hot-wall MOCVD reactor and the complete HEMT structure growth process have been presented elsewhere. 7,12 A series of AlGaN/GaN HEMT samples were grown to investigate the structural details in various AlGaN/GaN interfaces and their effects on the 2DEG properties. The series consists of three $28-nm-thick Al 0.17 Ga 0.83 N/GaN HEMT samples, denoted S1-S3.…”

mentioning

confidence: 99%

“…Besides, it is worth pointing out that a 200-nm-thick intrinsic GaN spacer layer grown at 1080 C with residual C, Si, and O concentrations below the SIMS detection limit of $1 Â 10 16 cm À3 was used in all the HEMT structures to prevent possible trapping effects and ionized impurity scattering that can adversely affect 2DEG mobility. 12 The samples were characterized by mercury-probe capacitance-voltage (CV) measurements to extract the pinch-off voltage. A contactless eddy-current technique and a Lehighton (LEI 1610) contactless mobility system were performed to measure the sheet resistance (Rs) and the 2DEG density and the mobility, respectively.…”

mentioning

confidence: 99%

Room-temperature mobility above 2200 cm2/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

Chen

Persson

Nilsson

et al. 2015

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