| A good lattice matching, and the carrier there of having a strong barrier properties, it is used for long-barrier layer and the surface of the barrier layer and In Al As, In Ga As,In As and other materials. HEMT devices corresponding to the same time as a large leakage current in the presence of defects, the requirement to form MOS HEMT structure, i.e. depositing the high-k dielectric layer on the In Al As layer so as to reduce the leakage, it is necessary for the electrical characteristics of the high k / In Al As to be the study. Al2O3 has good interface characteristics, Hf O2 has a high dielectric constant and Hf Al O can absorb Hf O2 advantages and improve the shortcomings of its low crystallization temperature, so a high k / In Al As MOS capacitor structures with these three types of high-k dielectric is focused on the study.Deposited by ALD technique in the In Al As layer, Hf O2, Al2O3 and Hf Al O form high k /In Al As MOS capacitor structure, the formations of these structures including etching the In As layer, pretreating the In Al As surface, ALD deposition of a dielectric layer, the dielectric annealing(PDA) and making the metal electrodes. The relative dielectric constant, trap density of interface states and the boundaries with the MOS capacitor structure of In Al As formed like interface parameters of different thickness of Hf O2,Al2O3 and Hf Al O can be extracted by analysis of the high-frequency C-V and binding assays ellipsometer. Content of each element and their presence in the form and with partial information can be obtained by XPS test. Studies have shown that in the different thickness of Hf O2 / In Al As structures, with the decrease in the thickness of Hf O2 dielectric, the interface and other properties deteriorating, mainly due to the lattice mismatch between Hf O2 and In Al As and In, As and O elements can spread into Hf O2 easily, which make the structures decline in the whole quality. While the analysis of different kinds of high-k/ In Al As MOS capacitors with the same dielectric thickness shows that comparison with Al2O3 and Hf Al O, In, As and O elements in more diffused in Hf O2. Hf Al O and Al2O3 have better lattice matching with In Al As than Hf O2, which improves the interface properties. But greater in the interface state compared to high-k/ Si MOS capacitor, which located in the order of 1012-1013 cm-2 e V-1.The study of Ileakage ~ Vg test curve and its deformation curve like lln I ~ Vg, ln(I / V) ~Vg1 / 2 and ln(I / V2) ~-Vg-1 curves depict that in the different thickness of Hf O2 / In Al As MOS capacitor, leakage current has a sharp increase with the lower dielectric layer thickness in the positive voltage. In the low voltage region, the thermal electron emission is the main model of leakage current transport mechanism. And the voltage corresponding to the thermal electron emission region decreases continuously as the thickness increases. While in the high voltage region, leakage current transport mechanism dominated by F-N and F-P models. In the negative voltage, leakage current less than the positive one, low voltage area dominated by thermionic emission, but high pressure dominated by the F-N and F-P models. At the same time, there is no much different in the value of leakage current between the positive voltage negative voltage of different kinds of high-k/ In Al As MOS capacitors. And their leakage current transport model is consistent with 10 nm Hf O2 / In Al As MOS capacitor. |
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