Processes to enable hysteresis-free operation of ultrathin ALD Te p-channel field-effect transistors.

Abstract

Recently, tellurium (Te) has been proposed as a promising p-type material; however, even the state-of-the-art results couldn't overcome the critical roadblocks for its practical applications, such as large I-V hysteresis and high off-state leakage current. We developed a novel Te atomic layer deposition (ALD) process combined with a TeOx seed layer and Al2O3 passivation to detour the limitations of p-type Te semiconducting materials. Also, we have identified the origins of high hysteresis and off current using the 77 K operation study and passivation process optimization. As a result, a p-type Te field-effect transistor exhibits less than 23 mV hysteresis and a high field-effect mobility of 33 cm2 V-1 s-1 after proper channel thickness modulation and passivation. Also, an ultralow off-current of approximately 1 × 10-14 A, high on/off ratios in the order of 108, and a steep slope subthreshold swing of 79 mV dec-1 could be achieved at 77 K. These enhancements strongly indicate that the previously reported high off-state current was originated from interfacial defects formed at the metal-Te contact interface. Although further studies concerning this interface are still necessary, the findings herein demonstrate that the major obstacles hindering the use of Te for ultrathin p-channel device applications can be eliminated by proper process optimization.