Fabrication of an InAlN/AlGaN/AlN/GaN Heterostructure with a Flat Surface and High Electron Mobility

The valence band offsets, ⌬E V , of In 0.17 Al 0.83 N / GaN, In 0.25 Al 0.75 N / GaN, and In 0.30 Al 0.70 N / GaN heterostructures grown by metal-organic vapor phase epitaxy were evaluated by using x-ray photoelectron spectroscopy ͑XPS͒. The dependence of the energy position and the full width at half maximum of the Al 2p spectrum on the exit angle indicated that there was sharp band bending caused by the polarization-induced electric field combined with surface Fermi-level pinning in each ultrathin InAlN layer. The ⌬E V values evaluated without taking into account band bending indicated large discrepancies from the theoretical estimates for all samples. Erroneous results due to band bending were corrected by applying numerical calculations, which led to acceptable results. The evaluated ⌬E V values were 0.2Ϯ 0.2 eV for In 0.17 Al 0.83 N / GaN, 0.1Ϯ 0.2 eV for In 0.25 Al 0.75 N / GaN, and 0.0Ϯ 0.2 eV for In 0.30 Al 0.70 N / GaN. Despite the large decrease of around 1.0 eV in the band gap of InAlN layers according to the increase in the In molar fraction, the decrease in ⌬E V was as small as 0.2 eV. Therefore, the change in band-gap discontinuity was mainly distributed to that in conduction band offset.

show abstract

“…1 6. Successful control of the molar fraction in MOVPE growth was confirmed for the thick InAlN layers by using x-ray diffraction.…”

Section: Methodsmentioning

confidence: 87%

“…Similar results have previously been reported. [6][7][8] In XPS measurement, only shallow parts of InAlN layers were probed as shown in Fig. 3͑b͒ for the samples with thick InAlN layers with 2DEG, resulting in no detection of the Ga 3d spectrum from the host GaN layer.…”

Section: ⌬Ementioning

confidence: 99%

Measurement of valence-band offsets of InAlN/GaN heterostructures grown by metal-organic vapor phase epitaxy

Akazawa

Gao

Hashizume

et al. 2011

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…1,2 To exploit the excellent properties of the InAlN/GaN heterostructure in a high-electron-mobility transistor (HEMT), leakage current through the InAlN barrier should be suppressed. For this purpose, the use of an insulator in forming a metal-oxidesemiconductor (MOS) gate structure has been proposed.…”

Section: à2mentioning

confidence: 99%

“…Measurement of interface-state-density distribution near conduction band at interface between atomic-layer-deposited Al 2 , near the conduction band. However, the MOS diode with careless interface formation resulted in degraded electrical characteristics, which indicated the process dependence of the interface properties.…”

mentioning

confidence: 99%

Measurement of interface-state-density distribution near conduction band at interface between atomic-layer-deposited Al2O3 and silicon-doped InAlN

Akazawa

Chiba

Nakano

2013

Applied Physics Letters

View full text Add to dashboard Cite

The Al2O3/InAlN interface formed by atomic layer deposition on a sufficiently thick silicon-doped InAlN layer lattice matched to GaN was investigated electrically. A metal-oxide-semiconductor (MOS) diode fabricated through careful interface formation showed a minimized leakage current and a capacitance-voltage (C-V) characteristic with a capacitance change large enough to evaluate the interface-state density, in the range of 10(12) eV(-1) cm(-2), near the conduction band. However, the MOS diode with careless interface formation resulted in degraded electrical characteristics, which indicated the process dependence of the interface properties. The effects of the acceptor-like interface states on the C-V curves are discussed. (C) 2013 AIP Publishing LLC

show abstract

“…1͑a͒ produced a 2DEG with a sheet carrier density, n S , of 2.2ϫ 10 13 cm −2 and an electron mobility, , of 1400 cm 2 / V / s, reproducing the previously reported results. 6 The obtained C-V characteristic for the Al 2 O 3 / In 0.17 Al 0.83 N / Al 0.38 Ga 0.62 N / AlN/ GaN structure is plotted in Fig. 2.…”

mentioning

confidence: 99%

Al 0.44 Ga 0.56 N spacer layer to prevent electron accumulation inside barriers in lattice-matched InAlN/AlGaN/AlN/GaN heterostructures

Akazawa

Gao

Hashizume

et al. 2011

Applied Physics Letters

View full text Add to dashboard Cite

The barrier structure in lattice-matched InAlN/GaN heterostructures with AlGaN-based spacer layers grown by metal organic vapor phase epitaxy was studied by the capacitance-voltage ͑C-V͒ method. To investigate the characteristics under positive bias, an Al 2 O 3 overlayer was added. The C-V characteristic of a sample with an Al 0.38 Ga 0.62 N ͑5 nm͒/AlN ͑0.75 nm͒ double spacer layer exhibited an anomalous saturation at a value far below the insulator capacitance under positive bias, which indicated electron accumulation at the InAlN/AlGaN interface. The C-V characteristic of an alternative sample with a single Al 0.44 Ga 0.56 N ͑1.5 nm͒ spacer layer did not exhibit the anomalous saturation. © 2011 American Institute of Physics. ͓doi:10.1063/1.3578449͔A lattice-matched InAlN/GaN heterostructure provides a high-density two-dimensional electron gas ͑2DEG͒ due to the difference in spontaneous polarization at the interface without any doping.1,2 To enhance electron mobility, an AlN ultrathin layer has been used as a conventional spacer layer.3,4 Several reports have been published on the application of the InAlN/AlN/GaN structure to field-effect transistors ͑FETs͒ ͑Refs. 3-5͒ including normally off type FETs.5 A recent study, however, reported that the insertion of an Al 0.38 Ga 0.62 N / AlN double spacer layer improved surface flatness and electron mobility compared with those for a single AlN spacer layer.6 Since the band gap of an Al 0.38 Ga 0.62 N layer is smaller than that of a lattice-matched InAlN layer, electron accumulation might occur at the InAlN/AlGaN interface under positive bias, resulting in a reduction in the effective barrier thickness. Schottky barrier diodes are not suitable for investigating electron accumulation in the barrier layer under positive bias. One of the methods of clarifying electron accumulation inside the barrier layer is to measure capacitance-voltage ͑C-V͒ characteristics using samples with an insulator overlayer on the heterostructure. In this letter, the Al 0.38 Ga 0.62 N / AlN double spacer layer is reappraised. A sample with an Al 0.44 Ga 0.56 N single spacer layer is also investigated as an alternative structure, for preventing electron accumulation inside the barrier layer. Figure 1 shows the structures of the test samples. An Al 2 O 3 ͑10 nm͒ / In 0.17 Al 0.83 N ͑10 nm͒ / Al 0.38 Ga 0.62 N ͑5 nm͒/ AlN ͑0.75 nm͒/GaN ͑2 m͒ structure and an Al 2 O 3 ͑13 nm͒ / In 0.18 Al 0.82 N ͑12 nm͒ / Al 0.44 Ga 0.56 N ͑1.5 nm͒/GaN ͑2 m͒ structure were fabricated and tested. The fabrication process of the test samples was as follows. Heterostructures were grown by metal organic vapor phase epitaxy. For the cap-annealing process to form an Ohmic contact, a 20 nm thick SiN x layer was deposited by electron-cyclotron resonance chemical vapor deposition using a SiH 4 / Ar and N 2 gas mixture at 260°C. After opening a ring-shaped window by lithography and wet etching using buffered hydrofluoric acid ͑BHF, HF: NH 4 F=1:5͒ solution, a ring-shaped Ti/Al/Ti/Au ͑30 nm/50 nm/20 nm/100 nm͒ Ohmic electrod...

show abstract

Fabrication of an InAlN/AlGaN/AlN/GaN Heterostructure with a Flat Surface and High Electron Mobility

Cited by 29 publications

References 15 publications

Measurement of valence-band offsets of InAlN/GaN heterostructures grown by metal-organic vapor phase epitaxy

Measurement of valence-band offsets of InAlN/GaN heterostructures grown by metal-organic vapor phase epitaxy

Measurement of interface-state-density distribution near conduction band at interface between atomic-layer-deposited Al2O3 and silicon-doped InAlN

Al 0.44 Ga 0.56 N spacer layer to prevent electron accumulation inside barriers in lattice-matched InAlN/AlGaN/AlN/GaN heterostructures

Contact Info

Product

Resources

About