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Thermopower Modulation Clarification of the Operating Mechanism in Wide Bandgap BaSnO 3 –SrSnO 3 Solid‐Solution Based Thin Film Transistors
Author(s) -
Sanchela Anup V.,
Wei Mian,
Cho Hai Jun,
Ohta Hiromichi
Publication year - 2019
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201805394
Subject(s) - materials science , optoelectronics , semiconductor , band gap , thin film transistor , electron mobility , transistor , electric field , figure of merit , effective mass (spring–mass system) , field effect transistor , nanotechnology , electrical engineering , physics , engineering , layer (electronics) , quantum mechanics , voltage
The transparent oxide semiconductor (TOS) with large bandgap ( E g ≈ 4 eV) based thin‐film transistors (TFTs) showing both high carrier mobility and UV–visible transparency has attracted increasing attention as a promising component for next generation optoelectronics. Among TOSs, BaSnO 3 –SrSnO 3 solid‐solutions ( E g = 3.5–4.2 eV) are good candidates because the single crystal shows very high mobility. However, the TFT performance has not been optimized due to the lack of fundamental knowledge especially the effective thickness ( t eff ) and the carrier effective mass ( m *). Here, it is demonstrated that the electric field thermopower ( S ) modulation method addresses this problem by combining with the standard volume carrier concentration ( n 3D ) dependence of S measurements. By comparing the electric field accumulated sheet carrier concentration ( n 2D ) and n 3D at same S , it is clarified that the t eff ( n 2D / n 3D ) of the conducting channel becomes thicker with increasing Sr concentration, whereas the m * becomes lighter. The former would be due to the increase of E g and latter would be due to the enhancement of overlap population of neighboring Sn 5s orbitals. The present analyses technique is useful to experimentally clarify the t eff and m *, and essentially important to realize advanced TOS‐based TFTs showing both high optical transparency and high mobility.