| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF+EM+MI-WeM |
| Session: | Thin Films for Microelectronics |
| Presenter: | Masaya Saito, Tohoku University, Japan |
| Authors: | M. Saito, Tohoku University, Japan T. Suwa, Tohoku University, Japan A. Teramoto, Tohoku University, Japan T. Narita, Toyota Central R&D Labs. Inc., Japan T. Kachi, Nagoya University, Japan R. Kuroda, Tohoku University, Japan S. Sugawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
We evaluated the difference of hysteresis in capacitance-voltage(C-V) characteristics of ALD-Al2O3 MIS capacitors for different semiconductors. N-type Cz-Si and n-type GaN wafers which had the bandgap energies of 1.12 and around 3.4 eV, respectively, were used as semiconductor layers for MIS structures. N-type Si wafer was doped with P of 5×1014 cm-3. The upper layer (2 µm) of n-type GaN wafer was doped with Si of 5×1016 cm-3 using a metal-organic vapor phase epitaxy. As the gate insulator layers of the MIS structures, the 10 nm-thick Al2O3 films were formed by the Atomic Layer Deposition (ALD) using Al(CH3)3 and H2O at 75 oC, followed by the formation of aluminum as the gate electrodes. MIS capacitors were irradiated by the light of white LED to only before the voltage sweeps of C-V measurements at -3 V followed by the voltage sweeps of -3 à 3 V and 3 à -3 V without irradiation.
We observed that the clockwise hysteresis in the case of Si gradually decreased as increasing the time of measurement. On the contrary, the hysteresis in the case of GaN was also clockwise and drastically decreased at the second measurement. It is considered that this difference was caused by the difference of bandgap energies between Si and GaN. In the case of Si, some electrons (holes) injected from Si substrate were trapped to the state near the Al2O3/Si interface when the positive (negative) bias was applied to gate electrode. When applying the subsequent negative (positive) bias, most of these charges were released because the bandgap energy of Si is small. In the case of GaN, most of these charges trapped to the state near the Al2O3/GaN interface were not released within the measurement time because of the interface states far from the both band edges owing to the larger bandgap energy of GaN. Therefore, the different hystereses for their MIS capacitors were probably caused by the difference that the trapped charges to the state in the bandgap were released in the case of Si but not released in the case of GaN.
Acknowledgement:
This research is supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan, through its “Program for research and development of next-generation semiconductor to realize energy-saving society. This work was carried out at fluctuation free facility of New Industry Creation Hatchery Center, Tohoku University.