Schottky barrier lowering due to interface states in 2D heterophase devices

Abstract

Interface states of metallic origin enhance the tunneling and significantly reduce the effective Schottky barrier height of phase-engineered MoTe2 junctions.

Assessing the role of quantum effects in two-dimensional heterophase MoTe2 field effect transistors

“…The same effect can, therefore, be created by gradually increasing or decreasing the carrier density in the semiconductor at a single metal-semiconductor interface. Previous ab-initio studies by Saha et al [20] and Urquiza et al [22] have investigated two different doping densities of T -H MoS 2 Schottky contacts and concluded that an increased doping density decreases both the barrier height and the depletion width, and our previous work [31] has demonstrated the same effect in T -H MoTe 2 contacts. However, to our knowledge, this is the first time the properties of these Schottky contacts have been investigated by gradually changing the carrier density.…”

“…The barrier height extracted from the DOS, therefore, represents an effective barrier for quantum transport, which does not necessarily coincide with the electrostatic barrier. This effective barrier will in the following be referred to as the DOS barrier, DOS , in agreement with the definition in our previous work [31].…”

“…The barrier height does not vary smoothly with the doping level but rather jumps between energy plateaus. Our previous work [31] and the work by Liu et al [25] have demonstrated that these heterophase MoTe 2 contacts host interface states, which increases the tunneling probability. At the interfaces investigated here, some of these states bridge the Schottky barrier and result in both increased tunneling probability and an effectively lower barrier than what the strength of the interface dipole dictates.…”

“…The wave functions are expanded as linear combinations of atomic orbitals using PseudoDojo pseudopotentials [40] using a cut-off energy of 100 Ha. The method is described in detail in our previous work [31] on similar interfaces where we also justify using PBE to describe these systems. Within this description, the H phase is a direct band gap semiconductor with a band gap of 1.03 eV and the T phase is gapless.…”

“…Ab-initio and first-principles-based methods have been extensively used to model 2D material-based devices during recent years [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. In our previous work [31], we have used ab-initio calculations to demonstrate how interface resonances at ML T -H MoTe 2 contacts create peaks in the transmission such that the Schottky barrier heights extracted by the thermionic emission model yield significantly different results than the Schottky barrier seen in the density of states (DOS). In this work, we go a step further and investigate the consequences of such quantum effects not only in the Schottky contacts but also in the T -H-T MoTe 2 transistors.…”