Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous....Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous. The binding energy and composition of the deposited thin film, obtained from the X-ray photoelectron spectroscopy （XPS） measurement, are consistent with those of SBA. The dielectric constant of the SBA thin film is about 50. Each of the capacitance voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and A1GaN. The interface trap density of metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT） is measured to be （3.5-9.5）× 10^10 cm-2.eV-1 by the conductance method. The fixed charge density of SBA dielectric is on the order of 2.7× 1012 cm-2. Compared with the A1GaN/GaN metal-semiconductor heterostructure high-electron- mobility transistor （MESHEMT）, the A1GaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However, the threshold voltage of the A1GaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from -5.5 V to -3.5 V. From XPS results, the surface valence-band maximum （VBM-EF） of A1GaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition. The possible reasons why the threshold voltage of A1GaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum （VBM-EF）, the reduction of interface traps and the effects of sodium ions, and/or the fixed charges in SBA on the two-dimensional electron gas （2DEG）.展开更多
An A1GaN/GaN metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT）, with sodium beta-alumina （SBA） for both gate insulation and surface passivation, was investigated and compared with a convent...An A1GaN/GaN metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT）, with sodium beta-alumina （SBA） for both gate insulation and surface passivation, was investigated and compared with a conventional metal-semiconductor high-electron-mobility transistor （MESHEMT）. The measured gate leakage current of the MISHEMT was reduced by approximately one order of magnitude as compared with that of the con- ventional MESHEMT. The saturation drain current of the A1GaN/GaN MISHEMT reached 830 mA/mm, which was about 43% higher than that of a conventional MESHEMT. The peak extrinsic transconductance of the MISHEMT was 103 mS/mm, which was similarly higher than that of the MESHEMT. The results suggested that the SBA thin film is an effective candidate gate dielectric for AIGaN/GaN MISHEMTs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50932002)
文摘Sodium beta-alumina （SBA） is deposited on A1GaN/GaN by using a co-deposition process with sodium and Al2O3 as the precursors. The X-ray diffraction （XRD） spectrum reveals that the deposited thin film is amorphous. The binding energy and composition of the deposited thin film, obtained from the X-ray photoelectron spectroscopy （XPS） measurement, are consistent with those of SBA. The dielectric constant of the SBA thin film is about 50. Each of the capacitance voltage characteristics obtained at five different frequencies shows a high-quality interface between SBA and A1GaN. The interface trap density of metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT） is measured to be （3.5-9.5）× 10^10 cm-2.eV-1 by the conductance method. The fixed charge density of SBA dielectric is on the order of 2.7× 1012 cm-2. Compared with the A1GaN/GaN metal-semiconductor heterostructure high-electron- mobility transistor （MESHEMT）, the A1GaN/GaN MISHEMT usually has a threshold voltage that shifts negatively. However, the threshold voltage of the A1GaN/GaN MISHEMT using SBA as the gate dielectric shifts positively from -5.5 V to -3.5 V. From XPS results, the surface valence-band maximum （VBM-EF） of A1GaN is found to decrease from 2.56 eV to 2.25 eV after the SBA thin film deposition. The possible reasons why the threshold voltage of A1GaN/GaN MISHEMT with the SBA gate dielectric shifts positively are the influence of SBA on surface valence-band maximum （VBM-EF）, the reduction of interface traps and the effects of sodium ions, and/or the fixed charges in SBA on the two-dimensional electron gas （2DEG）.
基金supported by the National Natural Science Foundation of China(No.50932002)
文摘An A1GaN/GaN metal-insulator-semiconductor high-electron-mobility transistor （MISHEMT）, with sodium beta-alumina （SBA） for both gate insulation and surface passivation, was investigated and compared with a conventional metal-semiconductor high-electron-mobility transistor （MESHEMT）. The measured gate leakage current of the MISHEMT was reduced by approximately one order of magnitude as compared with that of the con- ventional MESHEMT. The saturation drain current of the A1GaN/GaN MISHEMT reached 830 mA/mm, which was about 43% higher than that of a conventional MESHEMT. The peak extrinsic transconductance of the MISHEMT was 103 mS/mm, which was similarly higher than that of the MESHEMT. The results suggested that the SBA thin film is an effective candidate gate dielectric for AIGaN/GaN MISHEMTs.
