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A novel In GaN back barrier high electron mobility transistors structure with a compositionally stepgraded AlGaN barrier layer was grown by metal organic chemical vapor deposition on sapphire substrate.The structural and electrical properties of two samples were investigated and compared:the first sample is the stepgraded structure and the second one is the high Al structure as a comparison.By calculating full width at half maximum of XRD measurements,the densities of screw-type threading dislocations are 8.34×108cm2and11.44×108cm2 for step-graded structure and high Al structure,respectively,which are consistent with the results of atomic force microscopy.By Hall measurements,the measured two-dimensional electron gas mobility was 1820 cm2/(V·s) for step-graded structure,and 1300 cm2/(V·s) for high Al structure,respectively.The stepgraded structure improves the crystal quality of AlGaN layer due to the released lattice strain.The device was fabricated and leakage current is only 28μA when the drain voltage is 10 V; it was found that the In GaN back barrier could effectively reduce the buffer leakage current.
A novel In GaN back barrier high electron mobility transistors structure with a compositionally stepgraded AlGaN barrier layer was grown by metal organic chemical vapor deposition on sapphire substrate. Structural and electrical properties of two samples were investigated and compared: the first sample is the stepgraded structure and the second one is the high Al structure as a comparison. By calculating full width at half maximum of XRD measurements, the densities of screw-type threading dislocations are 8.34 × 108 cm 2 and 11.44 × 108 cm 2 for step-graded structure and high Al structure, respectively, which are consistent with the results of atomic force microscopy. By Hall measurements, the measured two-dimensional electron gas mobility was 1820 cm2 / (V · s) for step-graded structure and 1300 cm2 / (V · s) high Al structure, respectively. The stepgraded structure improves the crystal quality of the AlGaN layer due to the released lattice strain. The device was fabricated and the leakage current is only 28 A when the drain voltage is 10 V; it was found that the In GaN back barrier could effectively reduce the buffer leakage current.