Tetrahedral shaped recess channel HEMT with a floating quantum dot gate

For the first time in the world, we achieved, at 77 K, a transistor and memory operation of an FET structure which was grown in a tetrahedral-shaped recess (TSR-HEMT). This TSR-HEMT memory has a floating quantum dot (QD) gate at the bottom of the recess. Owing to the particular shape of the tetrahedral-shaped recess (TSR) structure, we were able to demonstrate that the charging of the floating QD gate can modulate the potential energy near the bottom by an amount of 9 meV and thus effectively modify the current. The measured I-V characteristics of the memory device clearly indicated a hysteresis at the sub-threshold gate bias region and a low power operation requiring write/erase voltages around only 1 V. The measured retention characteristics also showed that the device had a retention time of several minutes even at 100 K. We think that the TSR-HEMT is a promising structure for the use in future nanometer-scale microelectronics.