Bruzzone Samantha, Logoteta Demetrio, Fiori Gianluca, Iannaccone Giuseppe
Dipartimento di Ingegneria dell'Informazione, Università di Pisa. Via G. Caruso 16, 56122 Pisa, Italy.
Sci Rep. 2015 Sep 29;5:14519. doi: 10.1038/srep14519.
Research in graphene-based electronics is recently focusing on devices based on vertical heterostructures of two-dimensional materials. Here we use density functional theory and multiscale simulations to investigate the tunneling properties of single- and double-barrier structures with graphene and few-layer hexagonal boron nitride (h-BN) or hexagonal boron carbon nitride (h-BC2N). We find that tunneling through a single barrier exhibit a weak dependence on energy. We also show that in double barriers separated by a graphene layer we do not observe resonant tunneling, but a significant increase of the tunneling probability with respect to a single barrier of thickness equal to the sum of the two barriers. This is due to the fact that the graphene layer acts as an effective phase randomizer, suppressing resonant tunneling and effectively letting a double-barrier structure behave as two single-barriers in series. Finally, we use multiscale simulations to reproduce a current-voltage characteristics resembling that of a resonant tunneling diode, that has been experimentally observed in single barrier structure. The peak current is obtained when there is perfect matching between the densities of states of the cathode and anode graphene regions.
基于石墨烯的电子学研究最近聚焦于基于二维材料垂直异质结构的器件。在此，我们使用密度泛函理论和多尺度模拟来研究具有石墨烯和少层六方氮化硼（h-BN）或六方硼碳氮化物（h-BC2N）的单势垒和双势垒结构的隧穿特性。我们发现，通过单势垒的隧穿对能量的依赖性较弱。我们还表明，在由石墨烯层隔开的双势垒中，我们没有观察到共振隧穿，但是相对于厚度等于两个势垒之和的单势垒，隧穿概率显著增加。这是由于石墨烯层起到了有效的相位随机化器的作用，抑制了共振隧穿，并有效地使双势垒结构表现为串联的两个单势垒。最后，我们使用多尺度模拟来重现类似于共振隧穿二极管的电流-电压特性，该特性已在单势垒结构中通过实验观察到。当阴极和阳极石墨烯区域的态密度完美匹配时，可获得峰值电流。
